So, I was just thinking about something. Remember in Back to the Future III when Marty went back to 1885 and tore his fuel line? He and Dr. Brown then experimented with other fuel options to replace the gasoline. In the process, they tried whiskey and blew up the intake manifold (or something along those lines). Dr. Brown proceeds to explain that it will take him a month to rebuild it, which is an obvious problem, because, you know, pending death and all.
Dr. Brown arrived in 1885 via the DeLorean which he then hid in the cave so that Marty could find it in 1955, which he did, and subsequently used to go back to 1885. SO, there was a SECOND DeLorean available in 1885 Hill Valley that they could have scavenged the parts off of (and possibly even fuel, though one could speculate Dr. Brown drained all the fluids and either disposed of them or used them for something else). It’s even reasonable to assume all of that could have been done without destroying the timeline that would allow Marty to travel back in the first place to save Dr. Brown.
Ain’t time travel a bitch?