You have a Hayward SP26xx model pump -- see here:
http://www.haywardnet.com/inground/p...m?ProductID=10

Regardless of anything else, with 1.5" piping you are limited to about 40 GPM. I don't know what other piping you have, so I can't be sure, but a Hayward SP2607X10 should do fine. If you aren't budget constrained, a two speed SP2607X102S will save quite a bit over time, especially with a DE filter.

On your existing pump, I'd just knock the head off the screw and be done with it. Trying remove a rusted steel screw from an aluminum pump end (what it probably is) is not the best task to spend time on, when 2 screws will still hold your pump end bell on.

PoolDoc