New GM Corvette rear bumper skins are not available from GM now  now various quality  polyurethane ones.

This is for 84-90 models.

Probably the BEST preferred option is a Good used one..... media blasted and primed ready for refinishing. 

The are large items.. big coffin size boxes and flown in with our service parts fortnightly  AS NEEDED as deposited confirmed order is set up.

Time wise up to 4 weeks depending on ready stock in the USA.

Local delivery additional.