help with quench and head gasket thickness

[one low c10]

Have a question about an engine I am building and hope someone here can help me out! OK here is what I am working with...1979 350 block, I have taken to the machine shop. They checked the bore (4.00) honed, cam bearings, freeze plugs and hot tanked it. i have a new crank, recon rods, speed pro flat tops with 4 valve reliefs and a compression height of 1.56, comp xe268 cam, vortec heads, performer rpm intake and a holley 600 dual feed double pumper. the block and heads have not been cut at all. my question/problem is about quench. I am trying to get as close to .40 as possible. If I run a .015 steel shim head gasket am I cutting anything to close as far as piston to valve clearances or anything? should i go thicker just for safe measure? sorry about the long thread but Ive never put a motor together worrying about quench and compression ratios. Hope this makes sense and thanks for any help