I have been researching the 350 swap for some time now. The cost will depend on how fancy you want the swap to be...fuel injected new 350 with all the accessories (alt, pwr steering pump, harmonic blancer, headers.......) or you can pull one from a junk yard that is carberated (much easier)and it comes with all the accessories. I looked toward the 350 as opposed to other V8s because Advanced Adapters makes a bolt on engine mount for the 350 into a YJ. The tranny will probably have to be replaced too because of the extra power. You have a couple of options here. Autotrans 350 or 700R....manualtrans NV4500or many others that can work. If you want a real numbers you should order avanced adapters jeep conversion book and then start adding up the parts and finding prices. I'm on the five year program to collect everything I'll need. Chev 350 $500-1000, bolt in engine mount $200, wiring harness $$$, bellhousing adapter $500(guess), GM NV4500 $1000(junkyard guess), 23spline to 21 spline change to mount to NP231 transfer case $500 (guess), NP231 transfercase adapter $500 (guess), and then new drive lines because they will have to fabricated to the new lengths required by the change in the length of my 350-NV4500-NP231 setup $700 (guess). Oh yeah I almost forgot the inevitable short shaft kit for the NP231 $600 installed (guess). Again this is the five year plan that will probable happen in ten but I hope this helps. Anyone who sees it different please chime in.
87YJ I-6 Offenhauser intake Holley 4bbl MSD 6AL box