Damn you're good.....reading my mind now. 

 That was my next Q. I noticed some that actually use lengthened coupling type nuts, and bolt the plate to them. 
I prefer the access like you have.
I better ask this now....BEFORE you answer. 

The old J head I have has a little fat motor...1hp I think. Funny looking housing, never looked real close but is it pretty simple to change it to an inverter duty 56-C type motor ? And if using a VFD, do you typically leave the belt on one of the mid pulleys then just use the back gear if needed ?
Hah...beat ya to it. 

RC