Hi,
Yes, a bit of research after posting revealed the CA's different bellhousing bolt pattern. Point taken re: the Z33 box being much stronger that the CA / SR gearbox. I just happen to have a couple of CA / SR gearboxes lying around looking for something to be used in. Wouldn't be the end of the world if they wore out quickly.
However, the Z33 adapter sounds good. I might take a copy from you if I may in case I find a Z33 gearbox for reasonable money. If it's PayPal could you let me know the email address to send money to please?
Have you looked into a clutch, flywheel and starter set up at all? I have a lightened and balanced ST185 flywheel with slotted crank holes and the starter ring reversed. It be useful if it went down that route!