Hi waverider, and a warm welcome to the forum. I'ts great to have you aboard and always nice to have another Scotty owner with us on ODK
 grin

Here's how I would tackle your problem:
Purchase a new engine shaft key
After ascertaining the size of the shaft as Cyber Jack has explained, purchase a new model clutch half plus the 2 grub screws to suit....this will guarantee correct alignment and fixation to the shaft.
Put the machine back together and after adjustment (which we can help you with....Happy mowing! wink
cheers2

Please do not PM me asking for support. Please post your questions in the appropriate forums, as the replies it may receive may help all members, not just the individual member.
Kindest Regards, Darryl grin