Based on the images I could find online and my '77 sales brochure, this was the closest I could get to the stock look. The chrome bezel is way too wide and sticks out too far from the panel. The knobs are a perfect match, though.
The PO had also installed a RetroSound (pic below), but the AUX input was flakey - the left channel would drop out on a frequent basis. I have bluetooth in all my other cars and was missing it badly. Wife prompted me to pick out an upgrade for my birthday. Install was pretty easy - the newer unit was plug-compatible with the old so the wiring was already done. Needed to modify the holes a bit to fit the wider knobs. The rear knobs (chrome) still sit out a bit from the panel and from an angle you could see the cut-out holes. Fortunately, the install kit includes some black rings (not visible) that cover up that ugliness nicely.
BTW, the old unit is for sale. Works great except for the flakey AUX input. It is a Laguna and will come with the newer wiring harness, which IMO is a slight improvements on the older harness. Retail is $190...selling for $90 plus shipping.
Here is a link to the Laguna they have listed for Wagoneers, which will give you the specs, etc, but the pic directly above is the actual unit for sale, with knobs and faceplate.