I'll preface this statement with a disclaimer that this is merely my opinion:
Those pistons above would definitely work, and what's not to like? they're forged-and I'm pretty sure a modern version of the 6 pack pistons...
But I would probably pony up a little and use something like this:
http://www.summitracing.com/parts/pbp-12498-030/overview/make/dodge
They're only 730g without the pin...that's about the same weight as stock 340 forgings in the 68-71 HP engines. Reducing weight in the recip assembly is a good thing :thumblef:
In regards to the static CR, Assuming blueprint deck height (10.725"), the speed pro pistons come in at .021" in the hole. Those pistons with an open chamber head of about 88cc, .040"x4.4" head gaskets, 7cc valve reliefs, + 030" over, will yield closer to 9.3:1. If you drop the chamber volume down to 82cc (flat face valves, milled) and use a shim gasket, you'll achieve 10:1+...
The Probe slugs are roughly the same depth-(2.065" vs 2.061") and only 2 valve reliefs. Of course you can have your machinist shave the decks to zero the pistons up in the block and even with a fat fel-pro permatorque gasket, and the open chambers, would yield you about 9.5:1. Quench is of no concern/use in this app if you use your stock heads due to the rather deep chamber relief.
...no matter, even a 9:1 440 will still belt out 500hp with mild upgrades, and should easily drink low test fuel...and will create other problems for you...namely traction and worn downwind parts.