since you have a 94 you will need a newer style tranny.

best bet would be to pull a 6.0/4l80e combo with harness and tcase. i would go pre 04 so you dont have to mess with electronic throttle. i bet you can find the whole takeout for 2-3 grand.

the 8.1 harness is more complicated because its supposed to mate to an allison tranny so you're going to have a lot of work ahead of you. theres a guy on another forum who had this done by a pro shop and it took 3.5 months.

i would not suggest to rebuild the 454, it would not be worth the effort.

you'll also need a bigger fuel system than what the 94 has.