Driveshaft hitting cross member

[LS short box]

Hard to tell from the pics but it looks like you could raise the trans more than 3/4". I would shoot for around 3 degrees.
Too bad the CPP cross member angle cut the trailing arm brackets other wise you could drill additional holes to adjust the pinion angle.
I see that you measuring angles off the tail housing of the trans. I have found that measuring off the engine balancer gives a more accurate reading since its a machined surface.
Just another thought before you start cutting. Could the rear shocks have too much down travel? meaning could they be too long allowing too much drop?
My 68 C10 SWB had a 4/6 drop and I had to trim the top of the cross member.