Is it possible to put a Graflok/International back on a B&J Press Camera?
Bob, my instant reaction is that it isn't, but I could well be mistaken. Which size B&J do you have and what do you want to accomplish?
If you want to use roll film, getting an insertion type roll holder will be easier and probably less expensive than finding a Graflok back and doing the necessary surgery.
For a 4x5 camera with a spring back, Adapt-a-Roll 620 (must take up on a 620 spool, will feed from a 120 spool; I use 'em, respool exposed film on a 120 spool before sending it to the lab), Calumet C-2 and C-2n, and a variety of Sinar roll holders will slip into most spring backs. Toyo makes an insertion type roll holder that's 48 mm thick and may not fit your B&J's spring back.
For a 2x3 camera with a spring back, its an AAR 620 or a much thicker Toyo.
For what its worth, if the B&J is in reasonable original condition, I would not ruin it as an antique by messing around with it, I would just get a real Speed or Crown Graphic with an originalGrafloc back. JMHO