Pretty sure the intake is up under the cav. plate on that one, the suction cup muffs aren't going to work, double check before you buy the wrong adapter.
on the sides of the lower unit there is a slot on each side with some screens in them about 3/4 x 3 inches, right above the prop the is a rectangular hole the looks like it goes up into the lower unit. ???
No those are the exit, look up under just in front of the skeg, that would be the intake, actually not the skeg but under the cav. plate looks like a small skeg.
on the sides of the lower unit there is a slot on each side with some screens in them about 3/4 x 3 inches, right above the prop the is a rectangular hole the looks like it goes up into the lower unit. ???
Ok, lets try these, although 65 vintage I'm thinking it's what you have also. You'll see the external water adapter attached to the intake up under the cav plate.