Pinion Angle? Do I have this right before I cut it up?

For what it's worth, and my opinion only..... I would try the pinion angle shims before I went to the trouble of cutting the perches off. Summit sells up to eight degrees. As I understand it, you haven't driven it yet. I would at least give the shims a shot.
I run four degree shims with my super stock springs. I'm about five degrees down. Bracket car, with a 440.