When u say mm1 do you mean the older SEHP pump with built in lift piston? Because they also came with instaact pumps.
Cant speak to the SEHP but instaact just line up the slot in motor with pump tang, twist until it engages and the little locating pin falls into the holes. Get both bolts started then tighten evenly. Just make sure pin and bolt holes are clear or rust/debris