I made an old Graflex board adapter to fit my Sinar F1. I just took a front standard from an old Anniversary Graflex and disconnected everything but the Bakelite board and the board locking mechanism. Then I took a generic Sinar lens board, and used a Dremmel tool with a metal cutting disk to cut out a square hole, roughly the same size as the opening on Graflex front standard. Next I secured the Graflex standard directly over the square hole with some tape. Then I drilled some holes through the back side of the Sinar board and into the Bakelite of the Graflex front standard, careful to make sure they line up, but don't go all of the way through. Then I used a hole threading bit, to thread the holes in the Graflex standard, and used a slightly larger drill bit to expand the holes on the Sinar board. Make sure your pilot hole is big enough because you don't want to crack the Bakelite by putting too much stress on it. It will crack easily. Next I cut out some felt of the right thickness and size, and glued it to the Sinar board with rubber cement to plug any holes from any light leaks. Lastly, I secured the Graflex front standard to the Sinar lens board with some screws and washers.
I wouldn't worry about hacking a front standard off an old Graflex. There are plenty of them in the world, and many are in unrepairable condition anyway. So it's better to recycle the parts into something useful than throw them away, or let them rot in an attic somewhere.