Cylinder head decision for 318

As I have posted before, I plan on using a huges whiplash camshaft in my 318, the engine is a 1974 production and I am thinking about changing the heads. The only concern is the whiplash cam works well with stock compression and Im not sure how much more compression will rise with a set of performance heads. Also the engine uses flat top pistons and I also want to make sure there is no valve interference with the bigger valves. The heads im looking at are from indyheads, and are their Indy X series.
http://indyheads.com/images/maxlaxnewproductlinK.pdf

Looking to get better flow and bigger ports. If compression rises a tad would I still be able to run on pump gas?

Thanks