I assume this would be a little older motor? Chances are that you found the correct bolts, they just don't have the recommended orange/red gasket like the book says. How many times are those books right anyway?
My question though is: If you are having issues with porpoising, have you tried to install a fin? Otherwise known as a hydorfoil stabilizer? They don't fix issues on every boat but they are made specifically to get you out of the water quicker, up on plane quicker, and eliminate porpoising. Might be worth a shot.
I have OCD "Obsessive Crappie Disorder"