Kevin, PMFJI.

A while ago I got a lens made for a Koni-Omega to use on a 2x3 Graphic. Same problem as you asked about, the shutter is made to be cocked and fired by the camera body. I unscrewed my lens' cells and put them in the right size Copal shutter. #0, as it happens, and I had its aperture scaled for the lens. The 140 RB macro lens is, I think, in a #1.

You should be able to do the same with an RB lens. Coverage on 5x7 (210 mm circle) will be a little iffy below a little over 1:1.

I understand your desire to use what you have, but you might be better off with, e.g., a 150 Apo-Ronar (in #0 or front-mounted on an ex-Polaroid MP-4 #1 Press) or G-Claron (cells are direct fit in a #0), both for cost and for usable range of magnifications.

Good luck, have fun,