This next car has me scratching my head. And my leg. And my back...oh no, that might be fleas or bedbugs...but I'm still totally and completely and utterly flummoxed by this next car. On the one hand, I hate it when people shove carburated small blocks into classic inline-6 powered Jags, but I don't mind so much when they keep them inline-6 powered...but...an AMC 4.0 liter straight six from a Jeep? Find this 1979 Jaguar XJ6L offered for $4000 in Las Vegas, NV via craigslist. Tip from Rock On!
The RX-8 was Mazda's replacement for the out of production RX-7, introduced as a last chance attempt at saving the rotary engine. The RX-8 was built starting in 2003 and ending in 2011 when the lights went out on production of Felix Wankel's spinning machine...for now. Anyway, the RX-8 rapidly gained the a similar reputation to the RX-7 -- specifically that it was a great car to drive, but the engine blew up faster than a Miley Cirus relationship -- which was around 62 minutes after the first spark. So if you want to drive an RX-8 without worrying about your apex seals, you should swap in a Ford inline-6 from an F150. Right? Find this 2004 Mazda RX-8 with Ford inline-6 offered for $1400 in Minneapolis, MN via facebash marketplace.
This next car will invoke some serious "why would you do it?" and "why wouldn't you do it?" discussions with car guys. It could be the best car to meet your future inlaws and simultaneously the worst car to meet your future inlaws. A Toyota 7M-GE from the 80s also the best possible upgrade to a 60s Ford inline-6 and also the worst engine to put into your El Cami---errr--Ranchero. You be the judge. Find this 1961 Ford Ranchero offered for $4900 in San Diego, CA via craigslist. Tip from Rock On!
I was engaged with DT's Technical Editor CFlo in a spirited battle of "who drives a crappier wagon" (spoiler alert, it is CFlo) when I said with a twinkle in my eye, "you know what DT really needs?" "A 225 degree fahrenheit ethylene glycol enema?" "No...well...maybe...but what I was thinking is that it needs more classic Benzes that are grounded to the ground and powered by BMW inline-6s". "Oh yeah." Find this 1968 Mercedes-Benz 250S with BMW power offered for $9000 in Morgan Hill, CA via craigslist. Tip from Rock On!
If you are confused when BMdubheads get into their nomenclature, you are not alone. And you don't need to know the difference between an E36 and an E37 to understand the appeal of a rear-drive manual-transmission sport sedan from Germany. Find this 1989 BMW 325i E30 offered for $12,500 in San Diego, CA via craigslist. 
Time to wipe all history of the previously featured V6 powered MX-5 from your mind and start fresh like a Hillary Clinton e-mail server. This next car combines the gorgeous lines of the Malcolm Sayer & Doug Thorpe designed coupé (that is pronounced coop-A) with the silky smoothness and rock solid reliability of a Toyota / Lexus inline six. Find this 1989 Jaguar XJS with 2JZ power offered here on eBay
for $3,700 buy-it-now with 5 days to go, located in Ft Lauderdale, FL.
The Bavaria was the name for the bigger engine version of what BMW internally called the New Six (E3 sedan, E9 coupe) for the US market. It was eventually replaced by the E23 7-series, but for a few years (from 1968-1977) it offered a large executive sedan setup with a focus on fun for the driver. Find this 1974 BMW Bavaria 3.0 with E28 M30B34 Swap offered for $7,950 located in Atlanta, GA via craigslist. Tip from FuelTruck.
I knew this would happen soon. The E36 prices have gotten so low they are now being scrapped for their sweet inline-6 engines...it was only a matter of time. E36 M3s have been donating their engines to other BMW product for years (that is fairly common) but now they are starting to pop up in all kinds of Datsuns and now...for the first time...in a Sunbeam. Find this 1967 Sunbeam Alpine project with BMW M3 power offered here on craigslist for $7,300 in Rancho Cordova, CA. Tip from an anonymous commenter. 
The Datsun 240Z is a classic inline-6 powered 2-seater that needs little introduction to the typical motoring enthusiast. The stock engine was good for around 150 horsepower, so adding another 100 hp on top seems like a logical thing to do, but what if the donor engine wasn't from another Datsun, but hails from the distance continent of Europe? This is great if you like your sushi with a side of sauerkraut! Find this 1971 Datsun 240Z with S50 BMW M3 power offered for $11,000 near Atlanta, GA here on craigslist. Tip from Fueltruck.
The first generation RX-7 (SA/FB built in Japan from 1978 to 1985) was a beautiful ballerina in the sports car world. The RX-7's lithe frame was propelled by an equally dainty engine - the Mazda rotary. So, why would you take an RX-7 and power it with a cast iron block BMW inline-6? It is like casting a Schuhplattler dancer in the lead for Swan Lake -- she'll be great at jumps, but the landings will be painful. Find this 1985 Mazda RX-7 GSL offered for $8,000 in Hollywood, FL via craigslist. Tip from Greg S.
The PV444/544 was a passenger car made by Volvo for the post WWII car market. The PV was the first unibody automobile
from Volvo when it was first released for the 1947 model year and somehow managed to survive with little changes through the 1966 model year. Imagine cross shopping Ford's iconic Mustang and this piece of bathtub shaped 40s steel in the same weekend in 1965. What a hoot! The
PV444/544 was only ever powered by the Volvo's B-series inline four mated to the
rear wheels...but...someone managed to shove a tri-carb fed domestic inline-6 up front in this one. Find this 1963 Volvo PV-544 Inline-6 offered for $3,500 in Hamilton, OH via craigslist. Tip from Scot.
The E34 generation BMW 5-series was sold from 1988 to 1996 in the North American market and solidified BMW's reputation as a builder of sport-luxury sedans for the quasi-wealthy. The 5-series was not the ride of Rockefellers or rock stars, but it was the choice for doctors, lawyers, middle managers and folks who wanted a nice sedan with a touch of speed. Today the E34 is cheap enough to be the choice of window clerks at your local burger barn, but that shouldn't dissuade you from experiencing one of Bavaria's better built bombers. Find this 1993 BMW 525I E34 Touring with E36 M3 powerplant offered for $4,500 via craigslist. 
currently bidding on ebay for $1,025 with 3 days to go in Brooklyn, NY.
Regular tipper and SF Bay Area car aficionado Kaibeezy sent us a tip on a nice looking E30 BMW 3-series with a later M3 engine swapped into the front...but then he sent us two similar cars and we were presented with a dilemma. Which S50/S52 swapped E30 do we feature...and logically the answer is all three. Find these S50/S52 swapped cars, a 1988 BMW 325is for $14,500, 1987 BMW 325i for $12,500, and 1988 BMW 325is for $9,000 for sale in the Bay Area via craigslist. All tips from Kaibeezy.
The Mercedes-Benz W201 chassis was a compact luxury sedan from Germany and wasn't very sporty unless equipped in the 2.3-16V version with dog-leg manual gearbox. A gearhead could swap a different drivetrain into the W201, but we don't stumble upon them very often, so it is surprising to find this one. This 1991 Mercedes-Benz 190E W201 is powered by a Toyota 2JZ and 5-spd manual transmission swap and for sale in Reading, PA for $5,000 via craigslist. 