one of the fenders I just returned from Georgia with, still has a computer mounted, somewhere between 86-90 judging by the rest of the parts that came with it that match..... not sure of a year or what engine this would have had in it... what engine does yours have? got a number from the old computer? I had an 88 D100 back around 94, 88 was 1st year for that blasted Holley TBI system, that was my truck's downfall.... I spent more money good after bad on that truck, having to do with that 1st year EFI.... I sold that truck because I was sick of all that.... Ive driven big blocks and 360 powered, 4.10 geared duallies with no OD that were better on gas than that thing was.... my 79 Ramcharger with its fulltime 4wd (and of which I have heard many stories of past owners of those trucks that couldnt get over 8 MPG from) would return 14 MPG even..... my 88 was good for an absolute best of 9 MPG in day to day running around... 12MPG, at 70MPH on a solid, steady highway blast with a heavy tailwind.
looking back the best thing we could have done for it was to retrofit it to a carbureted setup, I might still have it if Id done that.