I am looking for a rebuilt or excellent condition 1980 differential with 3.55 or 3.73 ratio for my restoration project.

Pre batwing right?

ive got a couple floating around, let me see what gears they are. They'd need to be checked out though.

try James at northern corvette in St. Catharines area. Thorold maybe?

1980 is the one with the batwing.