Close Chamber or Open Chamber Heads?

Im going to be ordering a set of Edelbrock rpm performer heads for my 1970 340. Currently has stock pistons in it, may go to a stock bore, forged piston. I believe the 1970 340 had a compression ratio of 10.5:1? Is this correct? Can I use the closed chambered heads with the stock pistons or a set of forged pistons? (looking for 10.5:1 compression)
Also, what kind of horsepower can be expected out of the motor with a set of out of the box edelbrocks, 10.5:1 compression, Edelbrock rpm air gap intake, 750 cfm carb, a good size cam (.520ish on lift) and a set of TTI stepped headers? Thanks guys.