ok i got a question for ya'll

[68GMC454]

now i got a 68 1/2 gmc....thats my new toy...
now i got a 84 3/4 gmc with a 454 in it...

now i know it will fit in the 68,,i do have a 400 turbo tranny i got out of a junk truck..it shoudl drop right in with new motor mounts right...or is it going to be a pain in the butt...do i need anything from the 84 other than the motor mount and the radiator....i am really strongly thinking on doing this..so any info would be apreciated....mainly im just ready to start driving the 68...and the 454 is the only motor i got laying around..but i will know in the next few days on wether i get this mid to late 70's chevy thats runs with a god 350 in it...but am still leaning this way..i can always put the 350n in my 3/4..lol
billy