Stock '68 GTS 340" pinion angle question

Good morning,
When I bought my '68 Dart GTS, someone in the past had moved the springs in, rewelded the perches,f**ked up I guess because there were 5° shims/wedges between the spring and the perches,and put on some super stock springs.

I took all that sh*t off, cut off the perches, laid out the stock location and bought new perches.

My question:
Can I set my pinion angle while the 8-3/4" is off the car(it's at the body shop right now) and weld my new perches on level? It's a 100% stock application so I'm sure there has to be a degree dimension from when these rear ends were originally fabricated to be installed on the assembly line.
Everything is stock location. Stock K-Member, stock transmission and transmission mount and I'll be using stock replacement 1968 Dart GTS 340" rear leaf springs and have new stock location spring hangers and spring boxes
Thank you
Mike