Jeep Strokers

I am working with a shop to build my short block assembly, as well as the head work.

Using the 258 12-CW crank and the 258 rods, he told me if I cut to a .000 deck, stick pistons, w/ a .051 Head Gasket, my CR would be in the high 10's

He is suggesting a .02 deck with the same gaskets, equaling a CR of 9.5, and and a quench of .071

I know the gold standard is about a .040 quench, am I in ping territory at sea level?

Open up the chambers or dish your pistons my man. I would start with he chambers you can deshrouding the valves & open up the chambers a bit. Also polish em up really well with some high grit rolls & cross buffs. Polishing the chamber will help avoid detention as well.
Also a tighter quench may = more compression but because the quench is tighter it's kind of null/void. The tighter quench prevents detention so the added CR doesn't matter much. However a whole point may be too much.

Dishing the pistons will do the most.

I would strive for a tight quench and also caclulate your DCR because thats the number that really matters.