Iggy:

There should be a 4.5MT to MT3 adapter available from Clausing. I've
got 2 5913's, and they have the same spindle center hole as your new
(to you) Clausing.

If you'd like to make one, I'd be happy to loan you one of mine to
take measurements.

They are great machines. And my experience with Clausing's Technical
Support has been excellent.

_kevin