I assume you know that the coupe body is a FISHER BUILT BODY and the roadster body is a HERCULES CAMPBELL built body.
The body parts trunk lid are different as is most of the other roadster body parts. Coupe and cabriolet parts do not fit the roadster.
Most likely if you cannot find an original one , it will have to be hand produced using an English wheel and a skilled bodyman.
Possible the coupe trunk lid might only be to wide and too long, and can be cut down. The trick is, IS the curvature of the quarter panels the same
?? Its not on my 35 coupe vs roadster lid.
mike