Firstly, Welcome to Ribnet!
Single or three ram? (I guess single as its 1990) I'm basing theae commnts on the one(s) I've connibalised to get a working PT for my 60.
The two screws on the top of the motor will allow you into the brush gear, and if there's enough headroom probably allow you to get the armature out.
To get the motor off the pump / chassis there are 4 screws round the bottom (below the header tank / filler spout) and the whole lot comes out as one. (But you'll probably need to drop the whole unit to get at the two round the back)
Ishop marine has a few Microfiches which will give a better picture of how it's put together.