I'm rocking an 89 YJ with a tiny 2.5 and I'm looking to upgrade.  First I'm looking to drop a 318 in there but I'm wondering if my tranny and transfer case would hold up and if they even make adapters for it.  Also I'm looking to put dana 44s under it but I dont wanna get them and have them not fit.  I don't want to seem like an idiot but I figure I gotta throw caution to the wind and ask if anyone has any ideas about which vehicle I should look to rip everything out of and how much of a pain in the ass it'll be to put it all together.  Thanks for the help.  

Advance adapters will have the info and adapters for the swap, a more common swap is a GM small block. No, the tranny and transfer will not hold up very long. Neither will the driveshafts and axles, remember your adding a LOT of HP.  

The best doner truck for you is a 1979-1983 Jeep J-20. You get a bolt in dana 44 front, full float d60 rear and the running gear to go with it. I just bolted in a front and rear axle from a 83 J20. The front axle pad mounts are right on the money for the front. If I can do this swap, ANY ONE can. Don't bolt up a V-8 to the stock tranny, you WILL Kill it. You can always try and find a Eng/Tranny from a fullsize Jeep from 1979 and up and just bolt up the 231 t-case to it. I can talk you through the exact steps on swapping the axles since I just got done doing it. I can tell you the do's and don'ts and exactly what parts you will need as well as tools and equipment. I am NOT a fabricator or welder. But I was able to get it done in about 10 working days straight. If you get everything in order before you start, you can do it in about 5.