Duck - Its got to be the double groove style - the single has its single groove an inch too far back for a bird. The front groove (of a double) is closer to the same distance to the bolting flange as the Y-block. 
This photo shows one that has had its second groove cut off to make a Y-block sized single.
I have used the single 289/302 for testing by putting a one inch spacer between the pump flange and the inside mounting surface - like the aluminum disc at right below....
