you are going to love the power difference. Yes you can use the original radiator however you will need to cut your grill and make a bracket holder(its really very simple though). Ever thought of going to a dana 20 transfer case. Then you wouldnt have to change the output shaft. And as far as the input shaft goes why not use it? unless you are putting it in a cj5 rear driveshaft length isnt a bid deal(considering you dont have a goliath lift). But i have seen 904 automatics behind 401's is cj5's with 4" of lift. now dont forget if you started with a six popper in your jeep you will need to change the passenger side frame mount to seat the engine in there. Otherwise its pretty strait forward ive done it a dozen times and it keeps getting easier:) you dont need an adaptor for the t5 but you might want to check your pilot bearing size to make sure its the correct diameter, i cant recall if they used the same bearing but i doubt it(i think!) Anyways good luck and if you run into problems im sure some of the dudes in this board can surely help you! (OIIIO)