That's what I'm trying to accomplish on my firebird. I still want to do side pipes (headers) and a few other details. But for the most part aside from the driveshaft area the bottom of most vehicles are flat. I'm an American muscle car junky but I also lean towards BMW's, Audi (A6) but I still perfer my muscle cars.. I have a 1979 cloned Firebird (cloned into a formula TA) in my garage so you'd think my model would be pretty straight forward..lol. I'll post some refrence pics of the look I like in my "modeling" section.Yeh metal is correct steve, basically the interior of any sedan is a 'tub'. MOST modern cars (sedans) actually have a flat underside...everything is tucked away neatly, not like in the old days.
cheers bullet
P.S when are you going to do a 1967 Monaro buddy LOL