727 Rebuild Blues

Chk the pump stator rings off the pump and put them inside the front drum to make sure they fit the diameter ok. (Not to small to seal)
If I remember right there is a lip seal that can be mistaken for the right size inside the drum and if it's the smaller one, it will leak air pretty bad.
Assembling it on the pump and air testing like Tracy said will tell that quick enough.

Here's a pic for the rings and bushing topic, and the rings should be cast iron with interlocking ends.