You could feasibly fit a low profile double din unit (Alpine iLX-W650 or iLX-W670, just under 2.5" deep) in there...but it would be tight
and I'd wager you's have to relocate the HVAC controls above the radio to make it work. That could possibly raise another issue/whole set of problems.
Its been a while since I've been in that style dash, but there's an 88 sitting outside that I might be able to look at later this evening to get a better idea if it'd work.
EDIT: Just looked at a video...then checked the truck outside. I definitely think it could be done, but it might take a bit of trial and error to create a proper bracket. The depth isn't the big issue, as much as the width is. The stock unit measures 6.25" x 3.5" roughly. The overall opening is about 6.675". A double din is 'officially' 7" x 4". The HVAC controls could move down a small amount, but the bezel would definitely need a minor rework to fit the width. Definitely would require some 3d printing work, modeling, and a bit of cutting and splicing the bezel to make things fit. Then it's need to be retextured and finished.
Maybe consider using a marine radio? They're smaller (closer to 6.2 x 3") and might fit with a simple face plate adapter. Most are designed to be remote mounted as well.
- Kicker KMC5, Kicker 46KMC4
- JL Audio MediaMaster 50 [Unit: 4.65 in. x 3.74 in. x 3.15 in. (118 mm x 95 mm x 80 mm) Mounting Hole: 3.74in.x3.12in.(95mmx80mm)]
- Clarion CMM-20 [front panel dimensions: 5.95in.x3.90in.x3.15in.(151 mmx99mmx80mm) | cutout dimensions: 3.68in.x3.09in.(94mmx79mm)]
- Clarion CMM-30 [front panel dimensions: 5.95in.x3.90in.x2.95in.(151 mmx99mmx75mm) | cutout dimensions: 3.68in.x3.09in.(94mmx79mm)]
