This reply may or may not help as everyone has pretty much covered everything. But here is my opinion for what it is worth. I have a 96 K3500 7.4l truck that I am doing the same thing on and have done this on six other 7.4l. First I have found it is hard to find any to do a tune on a 96 or 97 because efilive and up will not work on it and since I currently building a 502 on for the truck I am not upgrading the current engine. With that said I ordered the Bosch injectors from eBay as I have had no issue with them in the past. I am replacing them fuel pressure regulator, hose, cap, rotor, plugs, wires, purge valve, and doing an egr delete and new K&N fuel filter. A small trick I learned is to use small zip ties on the fuel pressure vacuum hose.
While you have the upper plenum off, I would recommend replacing the intake gaskets and use permitex aviation sealant at the corners as the intake is prone to leaking at the corners.
If you are going to change the timing chain and take the 4 degree retard out of it, make sure to inspect the balancer rubber to make sure it has not slipped and/or is not coming apart.
If you have not started the work yet, I would recommend using a 3m three part fuel system cleaner. It comes with three different products to clean the fuel system, throttle body, and intake. If you are replacing the injectors, then I would do it before installing new injectors. Also remember to replace your fuel filter.
If you are interested I can send you the part numbers for the upgraded I was going to do to my 454 before I decided to drop in a 502.
