412 roof lining interior

[Oliver]

Hello,
On my '87 beaufighter 412, I'm trying to improve the interior. The roof lining was taken out from the central bar and hardtop by previous owner.
I've seen other 412's with round interior lights on the sides, mine's got wires dangling from top of bar through 2 rectangular slots - presumably where the lights slot in.
Has anyone got information or photo's of what it should look like, also what type of interior lights were used?

Thanks