Whatever you do, do one thing at a time. Changing heads and sideplate might be too much of a good thing.
Chances are your new bow has more zip than the old one. Pearson's were pretty nice bows, but not overly fast.
If you have a leather strike plate, carefully peel it up from front to back. Slip a strip of leather or a paper match stick behind it. Try to get it directly over the deepest part of the grip. Start thin and build slowly. It won't take much, most likely. The strike plate should stick back down enough to take some shots. Once you get it where you want it, use Barge cement or any good contact cement to reglue the strike plate.