It might be possible. Maybe. I mean, they both use the same CM845 engine controller. But what about the difference in piston cooling passages/nozzles with the ISB305? If you successfully reprogrammed a 255, might you not burn up a piston?
You'd have to blank out the JTEC module and the CM845, plus probably the transmission module if it's an automatic. I can't speak intelligently about doing this.