Keep my RB67?
20+ years ago, I kept a large RB67 system, with two bodies and a pretty much all the lenses. Eventually, with digital, I bought a back and the Mamiya adaptor. But the crop factor was useless for my work, and the lenses didn't produce the kind of resolution I was getting with film. I decided to sell the kit, and go with Hassleblad and some smaller formats. For me, the RB system has been outmoded for many years. It makes a nice, cheap introduction to MF film for students of photography, or for keen amateurs, but any digital solution for it is just too-clunky and limited for stress-free professional use - at least in my hands.
Given that the RB67 isn't the prettiest machine to own as just a display item, my advice would be to sell it for what you can, and move on. Don't expect a high price. I remember selling a body, film-back, auto-winder and a standard lens for about £400, 10-years ago. I can't imagine that prices have risen since then.