Thinken a head.Head gaskets.

You have to go by the actual Fel-Pro gasket part numbers because there are different thickness Fel-Pro gaskets that are "blue". The 1008 for a small block is advertised at .039", which is a popular thickness. Not sure if they have a thinner gasket, but using any thinner gasket is like milling the head. It will affect lifter preload and port/bolt alignment, but it depends how the alignment is with the current set-up. With factory tolerences, you can't take anything for granted. Then there is the question of will the compression gained by a .010 or .020 thinner gasket be worth the effort.

IMO, if you have the top end apart, stay with a reliable gasket and mill what's needed on the chamber and intake side of the heads to gain the compression you want and insure alignment.

Searching the Summit site for head gaskets will give you a list of different thicknesses and brands they have in the search parameters for comparison.