Quench means the top of the piston comes within .035-.050 of the head at TDC, once you figure in head gasket thickness and how far down in the hole the piston sits. There's really two kinds of quench. If you run a closed chamber head like a rebuilt/ported 915 or an edelbrock RPM / 440source stealth head and a flat top piston with a compression height of at least 2.060(KB237 would be a perfect piston for your build and cheap if you don't plan to run nitrous). When the piston gets really close to the head you get what's called quench. Having quench doesn't do much for producing more power, but it does allow you to run a higher compression ratio at the same amount of octane. Also a quench setup requires less ignition timing to get the job done.

The other type of quench setup is to run an open chamber head like a 906, 452, 346, etc any of the 1968+ factory big block heads with what they call a quench dome piston. With this style, the piston usually has a shorter compression height like ~2.03 or so, but has a tall 'dome' they call it. It doesn't really look like a dome to me, but you'll see it's a smaller raised area of the piston. The dome has to be machined to match up to the inside of your open chambered head. The result is with the dome and good machining, when the piston is at TDC, you get a similar combustion chamber shape as a closed chamber head/flat top piston combo, because that huge dome is taking up half of the space in the chamber. Needless to say, that setup requires some additional time spent measuring the dome, piston depth and cylinder head chambers and machining than the closed chamber style. With the closed chamber style all you have to do is mill the block's deck until the piston sits flush with the top of the deck, ie 0 down in the hole, then run a head gasket of about a .040 or so thickness and you're golden.

You don't have to run a quench setup, but it is beneficial, especially on a pump gas motor.

For the $ it takes to have stock cast iron heads, rebuilt, ported and bigger valves installed, you can almost buy a set of stock looking 440source aluminum heads, or a set of eddy rpm heads if you don't mind the aftermarket look. They will be closed chamber and flow as well or better than your ported stockers, plus the aluminum allows for more compression on pump gas. A 10.5:1 pump gas aluminum headed quench built 440 that runs on pump gas is easy. A cast iron headed non-quench motor will need to probably be around 9.5:1 to be pump gas friendly with a mild cam.

Also don't forget the 50lb weight advantage of the alum heads versus the cast irons.