What's the least expensive way that I can increase compression?
What's wrong with re-using the stock hypers, assuming they are flat tops? Realistically, how much would I have to mill the block to get to my desired compression ratio?
You'll just have to pick a set of pistons that are within your budget and go with a set of magnum heads. You want to look at the compression height (or compression distance) on the piston and pick one that is taller than stock (the distance from the center of the pin to the top of the piston).
Take your deck height and subtract the rod length, the compression height of the piston, and half the stroke and you'll get how far in the bore your piston will be and how much you'll potentially have to deck the block to get near zero deck. For $1500 you may get close but you might have to look for good deals or buy some of the Summit brand stuff, which isn't bad by the way.
The stock pistons are a dish design if I remember correctly....they're also about 0.060" in the bore......way down there and no chance for decent compression or quench. All quench does is allow you to run 93 octane on an engine with 10.5:1 compression by forcing the fuel mixture to the side of the chamber near the spark plug, where the flame is the hottest, the molecules are also more compact and energized, you get a better air/fuel mixture within the chamber, you get a more complete combustion, and a cooling effect across the top of the piston after ignition. So you don't need 105 octane or whatever the equivalent is.
These cop engines are talked up a lot, but they aren't that special performance-wise. Durability, yes.
You can use these web pages as tools to figure out which pistons to pick (by the specs given) and what you'll have to do as far as decking and head chamber selection to get the compression you want.http://victorylibrary.com/mopar/deck-height.htmhttp://www.csgnetwork.com/compcalc.html