Will the drivers side rear door from a 1991 Chevy G20 van fit on 1994 van?

It's *likely* but not guaranteed. While the Chevy G20 vans shared a lot of parts across model years, there's always a possibility of minor changes in body dimensions or door latch mechanisms between 1991 and 1994.

To be certain, you should:

* Check the VIN numbers: Compare the Vehicle Identification Numbers (VINs) of both vans. Similar VIN prefixes suggest a higher likelihood of compatibility.

* Compare door part numbers: Find the part number for the door from a parts catalog or online database for both the 1991 and 1994 vans. Matching part numbers indicate a perfect fit.

* Visual inspection: If possible, physically compare the doors. Look for differences in size, shape, and the location of hinges, latch mechanisms, and window regulators.

Without confirming these things, you risk buying a door that might not fit perfectly, or at all.