I made a couple of bars that bolt to the rotisserie head with some adapter brackets that bolt to the rails and are held on with 2" x 2" U bolts. This worked very well.
Here is a shot with the '49 frame installed.
A couple of weekends of cleaning and grinding and it was ready for paint!
This rig made it a breeze cleaning and painting the frame. Actually enjoyable, if you know what I mean.
******* Continued in next post *******