Under Body and Chassis Colors

helping a friend re-build his 68 GTX that's been sitting in a shed for 10 - 15 years.
he wants a basic or average rebuild of the car, not a all out resto.
staying with the factory silver color, engine compartment is painted, engine the correct color,pulled the 8-3/4 out and hot tanked it and backing plates. will wire wheel under side of body, should that be a body color, or a semi-gloss black, or should i use a under coating of some sort? springs,and housing ,semi-gloss?
needs a gas tank, just eave it natural?
is there post i could find some examples on?

primer with over spray of body color

If you're going to strip the underside, might as well refinish it like original, unless the guy wants it "hopped up": that means a medium grey color (unless it's an L.A.-built car, they were flattish black), with body color overspray from spraying the lower perimeter of the car, and then undercoating in the wheelhousings. If the car had factory undercoating, that's another option of course. Looks like the rad support is already blacked out.