Get as much as you can, better to have it and not need it. get the entire engine harness as you may need to change a few pigtails and the oil pressure sender on the 454 is on the front lower driver side of the block instead of by the distributor like the 350, so you will have to extend the wires...
My suburban is 90 and the 454 came out of a 91 1 ton truck
The trans has the beast sunshell, hd bands and clutches, corvette servo, new planetary set, new main shaft, and shift kit, there could be more but I don't know transmissions that well.
Still using the mostly stock tbi, I change the spring in the fuel pressure regulator to bump up the pressure, put in a wide band gauge and have been running fine. A chip might help but air fuel ratio is fine so I haven't worried about it.
30 over, procomp aluminum heads, 202/160, stock rockers for now, I want to try a set of 1.6's
Don't remember the dish on the pistons but it is 9.5:1 CR
I use this same trans cooler on both my trucks. Made my own lines, the feed line goes to the radiator then to the cooler before returning to the trans.