[JoeC]

do you have black interior on trim tag?

I think the chalk "B" on the firewall is black interior

My orange black top bucket seat 427 Chevelle has the same chalk marks on firewall
I thought "B" was for black top but yours has no black top
I don't think "B" is bench seat because it can't be for both bench and bucket

so I am thinking "B" is black interior maybe for black paint interior trim work