Would a C8OP cover be an acceptable part for a VIN-matching tranny in 69/70 gt500? Or would I be advised to continue the search in hopes of finding a C8ZP R cover(if there’s such a thing).
You can't search for something that was NEVER MADE. Casting numbers are assigned based on the original intent of the part. For another example your intake manifold says C8OE-C. Same for your cylinder heads C8OE-N. Many component parts were combined to make a specific assembly. IF a part was designed for and unique to a particular model it would have that model line as the third character.
The R servo with the C8OP casting number is correct for your car and you should also have the C8OP cast iron tail shaft housing. Those are the only two visual clues ( besides the metal ID tag) that could be scrutinized by ANY judge.
My use of caps is not internet yelling , it's highlighting important words. No anger here , just help.
Randy