you should only need three mounts the lower one on the seat down tube holds the pillow block and the motor mount you will nee to drill 2 holes for the engine plate. i dont think you will be able to fit all three on the seat down tube. maybe you have a different plan? looking foward to seeing your build!!! i will be posting pics of the schwinn soon been working on the gas tank and clutch. put in some different shoes for engagement hopefully it helps.
good luck
glenn
good luck
glenn