The two spoke VDM 356 steering wheels came in two sizes as well as having two horn rings.
Smaller wheels were in the roadsters and speedsters, slightly larger ones came in the coupes and some of the cabrios. Of course there was a lot of swapping around. The full horn ring is correct for all A cars, the quarter ring would be for '55 and down.
Just in case you can't find a source for an adapter, for the replica crowd, you could simply mention in the ad copy that a switch to the earlier Beetle steering shaft would work fine. For the full-tilt, use the column, column, bracket, rubber mount insert, blinker assembly and early style steering coupler.
With all of the above, you would have a nice, almost stock, looking set-up. Source a 356 clamp and blinker assembly and it WOULD look factory.
I have two of these wheels, and both style horn rings, and they're SO lovely. I really think that a nice reproduction would be very welcome and sell well to ALL 356 segments, including the VW community looking for a sweet "period correct" accessory wheel.
If you can come up with a GOOD LOOKING adapter, you would increase your marker share to include the entire VW community AND some of the genuine Porsche guys who want to back date the look of their B and C cars, at least interior wise. Just as the early 356s and VW's have the same spline, so do the later 356s and VWs.
Your idea just sounds TERRIFIC ! ! But PLEASE, PLEASE, let me know at least 3 months ahead of your release date so that I can sell my original VDM wheels while there's still a market for them. . . deal? OK ! !
Luck,
TC