A photo of your lock set would probably help. Sometimes a PO will change out the lock assembly with a different set. (Sometimes even a household type lock set.) Our '68 Overlander has it's original Bargman L100 with a long shank. The "vault doors" used in and around that time had the lock set moved inward a bit. Our trailer is documented here:
https://www.airforums.com/forums/f39...er-155180.html and there are a couple of photos on entry 21 showing some of the mechanism and the long shank. When you take it apart, you might want to photograph the disassembly and do it where parts can't get away from you. That will give you a guide (and hopefully all the pieces) when it goes back together.
If you need more photos, let us know,
Roy and Marie