Re: How bout a ford 390?
Yes, the 390 will fit in a CJ, the 390 was an option in the 67-69 ford mustangs, if you can fit an engine in an early mustang it will fit in a jeep. What problems will it cause? You will need front springs with much higher spring rates, go to a real auto parts store and have them look up the spring rates for a 1968 small block vs big block mustang. The 390 cast iron manifold weighs 110 pounds, aluminum less than 10 pounds. You can probably loose another 40-50 pounds by dumping the exhaust manifolds in favor of some small tubed Tri-Wye headers ( the headers will not help very much, just help trim the fat). The ford oil sump is exactly where it should not be, in the front, you may need to have suspension lift to clear the axle.
To give you some background I have a 466 cubic inch big block ford in a 1971 AMC AMX, so I have some experience with the ford/amc swap. Would I put a 390 in a jeep? Jseries/Wagoneer absolutely, CJ-8 yes, CJ-7/TJ maybe, CJ-5 never.
What would be my first choice for a short wheel base jeep?
4.3 V6, buick V6, 4.0/4.2 AMC six.
good luck, jjc