How much will 70cc heads raise my compression? Also how much lift?

And when it comes to time for a tear down and replacing Pistons I'm going to go ahead and make it a stroker is my idea, right now I'm going to get it together as is to get the car up and going, then I'm gonna build the bottom end in the future, stroker, girdle, cross bolt main caps, and nitrous. I'm doing a little at a time main goal now is to get the car running, get the chassis figured out and save up the money to do the bottom end. At first I was just going to run some ported iron heads then some budget opened up to allow a little more so it was between a bottom end rebuild, or heads, being I plan on a stroker later on, and the bottom end was fine i didn't see much sense in rebuilding a good bottom end for now just for basically a piston change while heads could help the compression some and really help flow a lot better than any factory heads would and can be used when I build the stroker. And I got a deal on the heads I couldn't pass up