Pinion angle severe but seems to be stock

[PORKY]

I’m getting back to work on my 1965 short box Fleetside Chevy. I have put new stock rear springs and bushings and it has a 295-50-15 Tire. The spring perches appear to be stock. The weld certainly looks factory. I have a 15 degree pinion angle, with the pinion pointing up towards the tranny. This is severe to me. The tranny angle is approximately 8 degrees pointing down towards the rear differential. I realize I need to pick the engine and tranny (zz427 & Tremec TKO600) up a few degrees. The front height of the truck is without the front sheet metal on it. But this certainly can not change the pinion angle that much. The truck originally had a 6 cyl. engine with a 3 on the tree. The front springs are new stock too. I feel I am missing something obvious and stupid. The angle is so severe the only fix seems to be to cut and change the perches. Has anybody seen such a severe pinion angle from the factory? I have attached a couple of picks showing the angle and the current stance.
THANK YOU!