You can get a junkyard 4.0 for next to nothing and a 258 for nothing, combined you can make a killer 4.6l I6 and everything will bolt up, tranny, electronics, belts, hoses, motor mounts, radiator etc.
I know it will be a bit more, but in the long run it'll get done sooner and all the little things add up on the V8 conversions. I have a TPI SBC in my CJ7, and it was cheaper to build a Chevy V8 than an AMC I6, but after all was done the I6 would have been the same money and a very cool engine with plenty of jam. A friend did a 4.6l I6 in a Grand Cherokee and it had a bit more than stock 5.2 Grands did, apples to apples comparison.