Ahhhhh....so you want it to look original, even under the carpets???
(me too...but don't tell anybody!)
underside of floor= satin or semi-gloss black.
firewall= as flat as you can get it. (heater box cover is fairly glossy)
interior of trunk: it varies. either black or red oxide primer (or both), then body-color overspray, then the trunk splatter paint.
interior of body: red oxide primer, then lots of overspray from the body color.
Check out Marks resto thread, I think he has pics of his floor there....correct overspray and all!
