The buckets might be close enough to work and maybe, just maybe the rear covers for a 68 Barracuda conv. might be close enough to work also. If you could find a 68 conv to measure the seats, that may give you an idea.
I have a good upholstry place that Has done alot for me and that was one of the options I was thinking. Might be the only way to go.
The only thing that worries me about all the measuring and all that is that once it comes down to it the fabric will not be fitting tight and looking as it should and for that I wont take the risk.