You should be able to buy the rear cam plug for B/RB and 426 Hemi block from any decent size machine shop, it is offered in both regular cup, and shallow cup. The size you need is 2 9/64, make sure and drive it all the way in to the stop ledge behind the cam I'm thinking your converter bolts or a converter bolt came loose and contacted the block, yes? If so make sure and debur the back of the block where the plug is before removing the old plug, I would also buy some 5 minute epoxy and seal the new plug to the block after it is in all the way Have you figured out how to get the old plug out yet without tearing into the motor Good luck