opinions on pinion/driveline angle

I'm asking for opinions on whether I need to change my pinion angle and how much. I measure the trans 5* down and the pinion 5* up. I'm thinking under heavy load that the pinion angle would be too high. I've got a 7 leaf rear springs with the top and the added leaf that are full length. I don't think they will wind up much being that short and that much steel.
The car is a cruiser not a drag car but we still like to have fun with it.
67 Barracuda, 340, 10.1, Edel heads, 545/555 roller cam, 3;23 gear, 5 speed. ~400+ hp I think.
I have a 4* shim in there and I was thinking of reducing it to 2*. I don't know how much angle the pinion angle might change under power or cruising.
I don't want to use a pinion snubber near the floor or lots of clamps or Caltracs, I'm after a stock look.
Am I over thinking it,,,what do ya think??

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