We will get into engine swaps in a lot more detail in a future article, but I will bring up this V-6 Buick swap for reasons that will be evident. By 1964 V-8 swaps were becoming common, with the Chevy small-block being the engine of choice. However, parental influence, insurance company policy, and the fact that I wanted to race in a particular class, resulted in not a Chevy but a Buick V-6. As it was, it turned out to be a good choice. Gary Hooker (of Hooker Headers fame) custom-built the headers for me, and Hick's Muffler and 4x4 shop added a set of tailpipes along with the then-popular, deep-tone Smithy's Glaspac mufflers. Offenhauser actually used my Jeep as a prototype for a new four-barrel intake manifold and Isky built a billet cam for it. I even eventually went for high-dollar Thomas magnesium adjustable rocker arms.
While it doesn't fit here with factory engines from Jeep, I had to mention this here because in 1967 Jeep decided to buy the V-6 from Buick and install it in the Jeepster and CJs. To some people it was the best engine ever in a Jeep. The 225ci limited the power output, but then it was found that the 350 Buick V-8 was as close to a direct bolt in as one could expect. However, there soon became lots of aftermarket equipment for the V-6. Chuchua, Offenhauser, and Kenne Bell offered four-barrel manifolds. Cyclone, Hooker, Jerry Jardine and Stan's had headers. There was a multitude of camshafts available, roller timing chains, and steel gears to replace the failure-prone nylon factory gears. There was even an extension plate for the exterior-mounted oil pump to allow the fitment of Chevy 409 oil pump gears.
By now the aftermarket was getting into the off-road scene. I remember when I first took my Jeep to Gary Hooker, the guys in the shop kind of laughed at my little V-6. Soon, however, the off-road bug bit them and they went on to produce hundreds of sets. They even built a few sets of headers for the four-cylinder F-head engine that next year. Jeep dealer and legendary Jeep racer Brian Chuchua figured there was still more life in the F-head, and in the mid 1960s he built a Roots-style, belt-drive supercharger for it. It was pretty pricey for the time and V-8 swaps were becoming more popular so not many were sold.
It wasn't until 1972 that the folks at Jeep figured if they wanted to be competitive against the Scout and Bronco they needed a better performance image, so they sold the V-6 back to Buick and offered their own 304 V-8. The AMC line of performance parts for cars was being developed, so they easily crossed over to the engines in the Jeeps. The invincible 232ci (later in a larger 258ci) also got its share of aftermarket performance equipment from companies like Clifford Research.
I believe Edelbrock built the first aftermarket manifold for the AMC V-8, and as luck would have it, the 304, 360, and 401 all shared the same block design so parts interchangeability was easy. While only the 304 version was offered in the CJs, in later years the 360 and 401 were available in the FSJs. However, Brian Chuchua's Jeep dealership was offering a complete factory-built 401 engine package for the CJs that included a high-performance ignition system, as well as a performance camshaft and Edelbrock manifold. Plus, it could be installed by the dealer in your new Jeep and covered by warranty!
As emission laws tightened across the nation and smog checks became mandatory in certain more-populated areas of California (to start with), numerous ways were found to beat the system. It seems that the Greens didn't care if the engine put out less pollution than it did before, fuel economy increased, or the highway mileage was limited, and modifications to the intake or exhaust were out. Registering your vehicle in another county or state was one way, or the widespread policy paying the inspector for falsifying the report was another. As fuel octane decreased, water injection became popular as a way to keep high-compression engines from self destruction. Through the efforts of organizations like SEMA, a compromise was finally met and today (with fuel-injection) we make more power and have cleaner engines than we ever did in the 1960s through the 1980s.
This Burns dual-carburetor manifold for the four-cylinder Jeep engine sold new for $26.50 in the 1950s and used Ford V-8 carburetors that were $5 rebuilt or $15 new. | 
At first glance someone would think that this was one of the very efficient early Corvette rams-horn exhaust manifolds. However, it's actually a stock Jeep F-head manifold, probably the most efficient piece on the whole engine. | 
Part of my performance package for one of my early Jeep's four-cylinder F-head engines consisted of a large single-venturi Chevy six carburetor and homemade headers. I only used them for racing because they came right up through the hood. |
This early Holley carburetor from a Falcon six was the hot replacement on both the L-head and F-head engines. | | |