Look for FG tabs in and around the bilge to see if they are delaminating. Baja had problems with that.

I have a 97 272 boss, Built a 500hp (dinoed at 542 hp.)Merc racing motor and it does around 75 . check for wood rott in rear seat, had to rebuild mine, yes they did have a delam issue on some boats, Check bolster bolts, I cut hand holes in the floor and put heavy plates under the floor and rebolted mine. I extended my trim tabs to 15" picked up some speed. I have been in 6'-8's on Lake Erie but Didn't like it at all. It will take 2'-3's fine good luck