a better tranny to drop in there is a 700r4 tranny. Its a newer GM tranny and you can find them with the driver side drop transfer case on them. Its a 4 speed auto and its accually pretty strong. I have heard of people converting to that tranny. its allot better. has a locking torch converter on it that is acccually programable. so you can set it to lock up for the most part. what that means is the auto tranny won't disengadge going down hills as much. It will stay in gear. allot better gear ratio in the tranny for both on and off road performance. I really wanted to put one in my jeep but the convertion for ford to gm tanny was more then i wanted to spend at the time, Still planning on it though. You will want to change out at least your back axle. cuz your going to break it with a v8. i broke mine liek 2 times. Changed over to a ford 8.8 axle off of a ford explorer. the best year of axle is 95 and newer. They come with disc brakes. the 8.8 is allot stronger then the dana 44 axles. You can go to http://mountainoffroad.com
and they have some info on the convertion and a kit for it to. as far as radiator goes the stock yj radiator will work fine. but if you want a really good radiator you can go to http://zandm.com
and they have a really good radiator there and some other jeep parts that they make. for the exhaust i would just go with shorty headers and then have a muffler shop run the exhaust out the sides under the frame right behind or in frount of where the leaf springs connect to the frame. they fix there pretty well and then run glass packs down the side and out in frount of the back tires. Thats how i have them on my jeep i will get some pics and post them on my jeep page if you want. just email me if you have any other questions.