They can be painted ... seal them with something meant to seal in smoke stains and then paint them with whatever.

If you are OK with losing a couple of inches of height, later you acn screw in furring strips and get a drywall over it.

Thanks LazyGardens --

Appreciate the help. I can afford to lose some height, I may just investigate the drywall option. I've got too holes like the one shown where old speakers were. I need to cover those anyway and they are NOT sized right or spaced right for my lighting plan.

If I can get the drywall done afford-ably -- I may go that route.

Thanks!