5 speed celica into V6 mk1

Hi all, I am in the process of fitting a celica 5 speed into my Mk1. Its all fitted in ok with a few mods to the tunnel, it was a old kit provided by the rod shop in castlemainesome 15 years ago. The kit came  with a solid 1 piece tailshaft complete with 2 uni joints (inside circlip type).  The problem I have is the rear uni jont on the supplied shaft (machined on the inside)  fits fine, & suites the internal circlip uni joint supplied, but the old original coupling to the diff from the 2 piece shaft has no circlip machined surface (it's pressed and punched to hold the uni in position). Is there a replacement coupling available or a mod to the old coupling????
Regards,
Mark