ahhhhh OK so that's some kind of TOUGH!He'll be mega tough and boiling him will make him more so. You can marinate him in some acidic marinade like lemon or vinegar to help soften meat fibers before BBQing him, but he'll still be pretty chewy. Most will slow cook an older bird. I've found canning them in a pressure canner the only way to truly tenderize a bird that old but I'm thinking a pressure cooker could do the same.
Thank you!