Really? You haven't heard that GM is one of the least customer-friendly manufacturers and they have all kinds of tricks built in to cost you money after the sale?
They became uncommonly selfish and stopped allowing us to buy their radio service manuals after the '94 model year because they wanted to lock up all that lucrative repair business for their two authorized repair centers. Then they found out that thanks to the 100 percent failure rate of their cd mechanisms, too many people were installing aftermarket replacement radios rather than spending around $450.00 through the dealer to get their radio / cassette players fixed. To combat that and increase their profits, which is more important than customer satisfaction and loyalty, they built the Body Computer into their radios. THAT is why your gauges and chime don't work. You can't remove the radio. When yours fails you can't even install a good used one from a salvage yard on most of their vehicles. Some radios can be reprogrammed to your vehicle, but only the dealer can do that, and they sure don't do it for free.
Also be aware the Body Computer is the master computer that tells all the other computers when to turn on. A dealership mechanic using the dealer's scanner has the option, from one of the drop-down menus, to electronically "lock" every other computer to the Body Computer. There is no way to undo that and you'll never know it was done until the radio has to be replaced. That's when you find out all those other computers have to be replaced and the software has to be installed in some of them over an internet connection. "Got'cha". This can render a vehicle "not worth repair", and even the people at the salvage yard can't sell those computers.
What you need to do is reinstall the original radio, insure everything works including power locks and windows, interior and all exterior lights, chime, and all other computers of which the instrument cluster is one. If you have to visit the dealer to have some computers unlocked, do that before continuing. If they see your new radio, they'll give you all kinds of excuses why you can't do that. Once everything is back to proper operation, you need to buy a "radio relocation" kit. That will have a wiring harness that allows you to mount the radio under the seat. That keeps all the Body Computer functions working. All you have to do then is cut the speaker wires and run them to your new radio's wiring harness.
If I remember correctly, there is no switched 12 volt wire running to the radio. There should only be a constant 12 volt wire. I might be wrong on that, but all the other computers, and especially if you have a remote amp, get their turn-on signals over the "data buss". The turn-on signal is broadcast on that buss by the Body Computer. When GM and Ford radios use a remote amp, they NEED an amp, and when they don't use a remote amp, they can't be used with one. Only Chrysler radios all put out speaker-level output. When remote amps are used, it's just for tone conditioning for the shape of the body. With your original radio mounted under the seat, I think if you leave it turned on, it will turn on the remote amp too, so assuming you leave it in the system, you'd connect the truck's speaker wires to the new radio's line output, not the speaker wires. If you don't have a remote amp, just connect speaker wires to speaker wires.
You'll need to run the 12 volt switched and 12 volt memory wires to appropriate places, but be aware the under-hood fuse box is another totally unnecessary but present computer. There are some functions that may shut down if too much current flow is detected. If that happens, try a different fuse. One thing GM used to do was provide blank terminals for accessories that owners added on. You might still find those inside labeled, "Ign" or "S12v" for the switched 12 volts, and "B+" or "12" for the constant memory 12 volts.
Saturday, March 14th, 2015 AT 9:29 PM