Yes, a tailgate from a later model will work fine. Last month I put a '93 tailgate on my '87 245DL for all the reasons you mentioned and because someone had kindly broken my rear window one night. It takes some real time, especially if you have to paint, but very doable. Yes, lock cylinder will transfer easily. The trickest part was the reatachment of the new tailgate, it's heavyish and unwieldly. I had the luxury of a forklift to lift it into place, otherwise a helper or two are definately needed. Check out archives regarding rewiring; rerouting the wires externally will avert future repair work.

I got my new tailgate, as well as four or five other small small parts, for $32 at local U-pull.

I still haven't gotten the latch properly aligned. It closes, but needs a good SLAM (ouch). Can't seem to quite get it right yet.

Good luck. 1987 245DL 228k