Might want to check the size of the chambers. They swirched to open chambers, but if memory serves, the 318 open heads until '71 were still only around 65ccs as opposed to the 340 70+. 302s tend to cc around 63-4. Least the few I checked did.
If thats true then you may not get much more compression unless you mill the head or use a thin head gagket. But you will also gain hardened valve seats and a fast burn conbustion chamber with quench.:happy10:
Mind you the best way to do a quench motor is zero deck with .034 or so quench. It makes for a very crisp sounding motor imho. They will still work without doing this,just not as efficiently.