(Decking) Whats the limit

I'm building a 408 stroker using 68cc RHS heads and .030 KB/Icon pistons. I need to keep it pump crap happy(91). Looking at the 27cc IC983's (9.1:1), there designed for the mag blocks with a 9.585 deck height vs the 9.599 LA. Which means I'd have to shave .030 to achieve zero deck for a desired quench of .039. Is this too much? How will this effect intake and gasket alignment? Should it be done to prevent distortion, two .015 or three .010 passes ?

I could go with IC745's (+20.5cc) and shave .010, but 9.6:1 will be high. This will be for a street driven 4x4 5,700lbs with o/d, 4.10 gears and 33" tires and 2200-2400 stall. I live in ND @ 900ft, even though its flat, it can often get hot and windy. I dont tow anything big 2500-4000lbs, but I still dont want to gamble since its my first motor.

Any thoughts or opinions would be great :)