Quick way is to hold them in place with tape behind the unit, that’s how they are done back in the day but that’s because they were surface mounted. Our problem is there is a void behind so on a previous Morgan I had a fun day in the garage one winter making a large flat washer in aluminium for every lamp to fit between the lamp and the rubber seal. This stops them falling back as when fitting the lense push back slightly traps the brass lugs against the aluminium washer. Could use plastic if easier to access, a slot means you can slip over the wiring to save disconnecting where you are not fitting lamps and just want to do the mod.
BR
Colin
