I've built a few panthers, a jackshaft set up would work. Why don't you want to weld the frame? Once you pop a motor on it it's going to ne devalued anyways unless you do a period correct motor say a whizzer . I think a HS with a jackshaft would look odd on a panther, I haven't seen one so I could be wrong.
and my stalled project
Norm from Venice would be the guy to check with on the fit, he has done a bunch of Panthers