To add to Steve's note above, a bit o' Goggling resulted in the below couple of leads...long shots but may be worth trying?.
1) Although not a new car dealer anymore Bean and Conquest appears to still be operating as an automobile wholesaler down the road from the original location..
Bean & Conquest Wholesale
61 Summer St
Bangor, ME 04401-6445
Phone: (207) 262-6000
2) The original Bean and Conquest's phone # (207) 945-9401 is still alive and in use by another Chevy dealer..
Maybe they took over the dealer code...and have old paperwork?.
Quirk Chevrolet Cadillac Of Bangor
293 Hogan Rd
Bangor, ME , 04401
PH: (207) 945-9401 | FX: (207) 945-0164
Good luck!.
~ Pete