I have a functional R.B. with a 4X5 Bausch and Lomb Tessar. It has a 3.25 by 4.25 back. Can one place another back on it, like a 4X5? Soon will be ******* on e-bay.

"With the right tools, one can make just about anything fit" so said the owner of a Volkwagen Beetle with a Ford 427cid mid rise in the front.

If the camera was built around and for a 3x4 back then it's best to leave it that way. The value is certainly in a complete original camera, rather than some horribly disfigured one..