Boy! Am I glad I posted this question. The plane with the 56 needed 4 OZ of weight in the nose to balance correctly. Running a heavier engine, I can remove the lead and gain the power. Don't need the 80 after all. Thanks to you guys, I learned the 72 will bolt in the same place. In contrast, I can't just deal with moving one motor mount over to fit the 80, as the engine would then be operating off the centerline. Not good. Using the 72, wont have to center the engine, which means I don't have to pull the hatch and modify from there. Now to find a 72 I can afford.
Thanks for the rapid response. Oh yeah, the 80 has 1.3HP and the 72 has 1.2HP, but less weight.