Really, if you are handy making brackets and splicing wires, any stock ish head unit could be made to work. The GM size in these (and 90's ) trucks was Din and a half, not double din. There are a COUPLE of aftermarket radios for this size that you could look into. Really, even if you don't like aftermarket stuff, there has to be one out there you could live with. Putting in a stock one would be more effort than an aftermarket one. Aftermarket one you just buy a dash kit and wiring kit (if you don't want to cut factory harness) and mount up. You can find some CHEAP aftermarket ones now too, with USB or AUX in for an ipod.
But if you want a stock one, as long as oyu can hack the plug off whatever you take it out of (the plug that goes inot the back of the unit), you can make just about anything work. Just standard constant hot, switched hot, ground, illumination, antenna, and spkr wires. Not rocket science.