I had a '67 Jeep Commando with the optional V6. It was a 225 Buick engine, and I think I recall that the Buick (350?) V8 was available in the full size Jeeps of that era.
When AMC took over they put in their bulletproof (7 main bearing) straight six, and the 304 V8. The six was available in displacements of 199, 232 and 258, but I think they only put the 258 in Jeeps. In the full size Jeeps you could get the 6, or the 360 or 401.
In 1980 they started offering the GM "Iron Duke" four cylinder in the Jeep and some of the cars. It was kind of gutless, but durable. In '82 they made some changes to the 6 cyl, lightening it up by 90 pounds. (Only available as a 258 by then...) I recall that we could never get that plastic valve cover to seal very well. It only had two screws to hold it on, located in the top of the valve cover, so we would pull it off, silicone the joined area, and the put the cover back on with very minimal torque on the two screws to avoid warping it.
I was not only an avid Jeeper back then, but actually worked at a dealership selling them. We used to have a lot of fun scouring the junkyards for parts to build Frankenstein six cylinders. There was one year, ('67 I think) that a six cylinder in an Ambassador had a two barrel manifold. That manifold with an adapter and a small 4 bbl carb, a split exhaust manifold (or a set of headers), 232 shortblock and 258 head (short stroke, big valves) was a gutsy combination.
Personally, I would look for an AMC six cylinder prior to the plastic valve cover model.
