What kind of heads do I have?

I'm building a 318 right now as well and have done alot of research on pistons and if you have the money then yes you can boost compression with pistons kb has a piston with a compression height of 1.810 which would put you about .01 below the deck without machine work assuming everything is stock. For a price tag of around 450 with rings!
If the OP is not building a race motor I'm sure he could get some custom piston made for less than $450??