I have one. But its installed in an 81 Suburban. You can buy the whole truck for $2900. It runs but needs a valve job I think as it's got a little skip at idle, intermittant that I don't think is ignition. 454 - T400.
The Gear Vendor in it needs a rebuild by Gear Vendor, bout $400 I think they charge with the updated electronics. Better than 2K + for a new unit. You could pull the Gear Vendor out and put a stock driveline back (which I think I still have) in the truck and probably get the GV for very little that way. I don't have time to screw around with it though just want to sell as is. The Sub would make someone a good work truck with a little mech work on the motor. It is currently filed non-op status which is how I'd want to sell it as I don't think it'll pass smog without fixing the idle miss.
Btw this truck is painted red, decent paint job, would look good for a work truck capacity, although no longer show quality paint (few chips, normal wear and tear). Good tires (stock wheels), dropped 3 in the front 2 in the rear, 2WD, aftermarket front bucket seats (nice ones, Kustom Fit make I think). And it's got a later model (1990) front clip and GMC Grill with the later headlights than came with 81.