I have a 78 ODay and have had no luck in tying to match up my flange cause it's a 3 hole too....in the Buck Algonquin catalog they don't list my flange under my transmission which is a Paragon but the only 3 hole I've found is listed under the Atomic, I don't need one now but when I do I'll probably let a propeller shop help me, maybe try that route