It's your model Ron, do what you want with it man, after all, we build those things to have fun!!
The wheel painted in white will look good with blackwall tires, yes they will.
if you want to detail it to look more factory, the interior gray is a medium gray tone.
The floor pan was painted at the line before painting the body itself on cars that would go to places where some more rust protection were needed.
A curious fact is that if they had just painted a Colonial Blue car, for example, and the next car on the line needed to be painted a different color, they would empty the paint guns at the floor pans, so you could have a Raven Black car with a Colonial Blue floor. Usually, cars that would be sold in states like Arizona, or California would have just the red oxide primer on the floor pans, with some body color overspray, and black undercoating on wheel weels, and rockers.