The lens came on a lensboard too big?? I can't imagine that, as all the Horseman 6x9 cameras, and even the 4x5 field cameras take the same lensboard. The lenses come near permanently attached to the boards with the synch cable and actuating mechanism for the solenoid.
65 and 75 share the same infinity stop, so both need to be on the same style lensboard.
VH-R takes either style lensboard (early or late) but if you are sharing the infinity stop between the two lenses, they both need to be on the same lensboard type (so the flange focal distance between the two is the same).
This, of course, only applies to use with the rangefinder. If focusing on the Ground Glass, the lensboard does not matter.