There were also a couple of years of full size Ford and Mercury, as well as Thunderbirds (and I think Lincolns) that had a 428 engine. Was pretty common as a police motor around 1966-67. Not a CJ, but a workable block.

An option is to take the 390 block (4.05 bore) and fit it with a 1U crankshaft. This yields the Merc 410, which isn't a bad setup. The one I'm building for my pickup is bored .060, for a total of 4.11 - close to the 4.13 of the 428. 1U crank was also used in the 428, so I'm at something like 422ci at this point. It ran well when taken out of the car, only prob was premature failure of a cheap timing chain (stretched - timing was erratic). Had the CJ/390GT cam and 390GT intake and exhaust, and was pretty strong.

I know DennyW makes a lot of power with his 410...