According to an email reply I got from Powroll, the head and cam of the Grizzly 350 and Raptor 350 are different and they are not sure if there would be interference issues with using their 365 cc piston in a Grizzly.

Does anybody know if the Bruin350 and Grizzly350 have the same head, cam and piston? Are there any manufacturors who are currently making a big bore piston for the Grizzly 350? I can find high compression pistons and cams but haven't found a big bore piston yet.