which globes are the correct ones?
Both top and bottom of the stop/tail lights use double filament globes in all VN and VP. The pin heights are different between single and double filament globes so you'd have to force a single in but as ^^, ^^^ it does happen.
I see from your sig. that you have an early VN so both top and bottom will originally have lit as stop lights. Later in VN, and also VP, only the top lights are wired to light as stop lights (lower are park only) but are still double filament globes.
It is possible that the tail light harnesses in you car have been replaced at some point with the later type, so if the lower lights don't work as stop lights, it may be no problem. You can also tell by looking for there being only a single connector terminal, in one of the two holes, at the base of the socket for the globe.
All the other tail light globes i.e. reverse and indicator are single filament.