TOM, what type do you want? 49 merc has 5/8 belt, 50&51 has 3/8 belt ,49-51 merc,s have the motor mount like a 37-48 with a vertical bolt , 52 and 53 are like a 49-53 ford, 49-53 ford is a complete different pump than a 49-51 mercury, the motor mounts are underneath at an angle and 49 is 5/8 belt and 50-53 is 3/8 HENRY