OK I am sick of not having enough power in my stock 258 4.2L (w/weber). (See my CJ specs below) I have thought of the 4.0 head conversion with Mopar kit but the final cost is close to $2800 to 3k. I have thought of swapping to a GM engine but what cubic inch I'm not sure which one or a 1997 or newer 4.0. I would like to end up with at least 200-210HP. What GM engines are the most popular swap? Will newer 4.0 OBDII engines directly bolt to the same bell housing as a 4.2? Any other suggestions on swaps or ? along this same subject.

78 CJ7, 83 wide track axles/Dana 30 Front W/ OX Locker, Model 20 rear w/ one piece shafts(welded tubes)/Detroit Locker, 4.10 gears. 4.5" spring lift with 3/4" shackle lift. 35x12.50 BFG MT, 4.2L, Weber Carb, K&N, T18,Scout Dana 300,Warn 9.5ti