64 C10 Half Ton Pinion Angle/Adjustm

[Leverhead]

Hello all. Building a 64 c10 half ton using an L31 crate/700r4 combo with CPP tubular trans mount. Pinion angle at the diff is showing -1 at most. Noticed the stock perches at the trailing arms point the diff up a bit. Anyone know what the stock pinion angle was and what available options there are to adjust the angle if necessary....shims maybe? Seems the rear mounting method on this truck with the trailing arms wouldn't allow the diff to much when under power anyway. Plan on lowering and bagging in the future and cant see having to weld new perches any time the ride height is changed. I could shim the trans mount but it would have to be a lot of shimming to change the angle and the engine is currently sitting about right (3-4 deg) with the manifold/carb mount level. Any ideas or info appreciated.