Ribbed trim panels means 81-85 so a Diesel would be a 300SD. Plain trim panels means 86-91 so a Diesel would be an 86-87 300SD or 90-91 350SD/SDL.

That looks like a 126 gasser gauge set (Diesels don't have a vacuum gauge) since there's no fitting for the mechanical oil pressure gauge that would be in a 123 gauge set. At least I think all 123s have mechanical oil pressure gauges.

The 124 gauge board includes the illumination and turn signal bulbs - left side integral, right side on a pigtail. No way that's a 124 board.

I suppose you can transfer the mechanism. I'll check the PNP here the next time I go. The $7 or so I paid for the gauge panel means doing custom work had better be a really easy job.

Sixto
87 300D