Regarding hardware for installation of the under dash lamps (all 63 and 76 body examples and optional for 65 body examples), the assembly manual suggests using existing hardware on non AC cars (glove box door, right-most bolt) and to use 374121-S2 for the LH side of both AC and non-AC examples. The AC cars (w/factory Select-Aire) for the RH Courtesy lamp, all used the shorter lamp bracket, the same as the left side uses. AC cars are mentioned in the AC installation instructions of the 67 Electrical Assembly Manual (page 89 E7-8655-8, lh lower corner) to use the same screw 374121-S2 that is also used on the left hand Courtesy light.
It might also be noticed that NO DETAILS are given for this particular bolt in the Library Spreadsheets as to dimensions of this bolt mentioned in the Electrical Manual.
Another note, not all installations of the RH Courtesy lamp, non AC cars, used the recommended glove box bolt (existing hardware) as Jeroen's example shows but instead, mounted into another hole to the right if the glove box hinge.
One other note, unrelated to the Courtesy lamp, some glove box hinges attached using a nickel-sized flat washer and some do not.