I bought my mounts from a parts house company called Mopac, they were 75 bucks after tax, and obviously came from someone's garage
Far from beautiful like S&Ps shiny ball beveled things, but they get the job done, and look factory after being installed.
Wiring is also a super easy thing to do, just use the factory harness, and you only need to change one pin from one location to another, then add splice in several wires from your factory harness.
Programming involves removing VATS, and any emissions systems you are not installing.
www.pcmamerica.com has the best price I've seen out of a programmer to date.
As far as gauges go, you can buy / build adapters for both the factory 73-87 sending units, and you can install an electronic speedometer from a 90-91 Crewcab, Suburban, Blazer, or Jimmy, as they use the same 40 tooth reluctor ring sensor in their transmissions as the 4l80e, and 4l60es do, just splice the factory DRAC + speedo in along with the PCM, they are just fine sharing the signal from the VSS.
I'd personally use the newer truck's aluminum radiator + overflow bottle to avoid issues with steam lines, and rad hose exits etc. Both them, and the factory fuse block can be mounted in these trucks as if they came that way from the factory.