Which Valve Angle to grind

I'm building a GSR motor slightly stroked with an LS crank Eagle rods, and Endyne high compression pistons. Compression will be about 12-1. I have portflow Inner springs and retainers and ITR outer springs (all come with their kit). I'm debating on whether to use aftermarket SS valves or stock ITR valves. I'll be using a stock GSR intake manifold and stock throttle body with a 2.5" cold air intake. I'll have a 4-2-1 header but the rest of the exhaust system will be stock.

I'm getting a 3-angle vavle job while the engine is at the machine shop, so what angles should I have the vales ground to for this setup? Anyone with a flowbench know what works well? Thanks for any advice you can offer in advance.

not sure of exact numbers, but the machine shop should have some specs as to what he will cut them too.

I'm looking for specific angles. I'm sure he can just do the standard 60, 45, 30 degree cut, but a guy with a flowbench once told me that altering the angles can gain you a few horse depending on what else you've done to the motor. Whadda I know? He may have been on the crack pipe.

Thanks