I have a 68 that has benn cloned into a 400. The 400 has the old style 8 bolt waster pump. I pulled it due to rising water temp at idle and was checking out the plate-to-impeller clearance. Anyway, the bottom,or first plate is there, but the second piece is missing.Does anyone know what the purpose of the 2-piece design is? Also, I've noticed the 2 inserts that sre in the parts catalogs. Do those need to be there also? If so,where exactly do they go?