Sorry to have taken so long to reply. Much to do after renters left our other home in a shambles...Anyhow, a bit of history on the components.
The 454 originated in a 1974 "Heavy Half" Suburban that had a Turbo 400 behind it, two wheel drive, of course. I installed a new flywheel, clutch assembly, pilot bushing, and put it in front of the 465 where a 350 gas engine had previously been. The 350 had a connecting rod hanging out the side of the block, courtesy of one of my sons who had an "enthusiastic" driving style.
Prior to installing the 454, I replaced the timing set with Cloyes double roller timing set, and while it was on the engine stand, I removed the oil pan, R&R'd both front and rear main seals, inspected the bearings, and put in a new Melling HV/HP oil pump and drive. Other new parts installed were water pump, thermostat, Accel HEI distributor, coil, plug wires, fuel pump, power steering pump, and I removed the remote engine oil cooler adapter from the block that I never could get to seal. I should have replaced the cam, lifters, springs and retainers, and also should have had a valve job done, but it ran really well prior to removing it, so I figured why...
Another son with the same right foot affliction as the other, soon revealed why the original valve operating system was inadequate! It now has lifter noise in at least a couple or three lifters. For now, it's just an annoying 'tick', but I won't let that get too far along before I remedy it. Also purchased new and installed into the GMC was new motor mounts, intake manifold and exhaust manifold gaskets, a new, properly sized and rated "big block" aluminum radiator and mounting pads, as well as new hoses.
I "kitted" the "Quadraflush" carburetor, which starts, and runs great, seems to be quite capable when 'wheeling, and has yet to develop the "overnight fuel dump" that every other Quadrajet I've owned has eventually developed. I do have a 650 Edelbrock carburetor that I had been running on a small block, and I'm going to swap that for the Q-jet to see if there's any difference in performance or mileage before I get to yanking and swapping drivetrains.
The 3/4 ton axles are geared 3.73, and both are "open" differentials. Both have had new rotors/drums/pads/shoes/bearings installed within 10K miles, with no noise, vibration, leakage or other distractions noticed in operation.
As I plan to 'gut' the pickup to acquire the parts to make the swap, the pedal assembly, steering column, and all the other little parts that can be aggravating to find are 'right there' and work, so I'm not anticipating a big parts search, with one glaring exception...I'd love to dump the NP208, and install the NP205 that I have sitting in the corner of the garage. Problem is that the 205 came from a Dodge 3/4 ton, (transmission unknown) and I'm not sure about compatability. I may end up putting it in the paper with an offer to trade for the 'right' GM case.