With cast iron heads, 9.5:1 is about the most you'll want in compression ratio if you want to run any kind of advanced timing without it pinging. 10.5:1 if you have aluminum heads. Something in the range of a .480 lift and 280 duration should be fine with those gears, carb, and intake. Maybe a little more if he has headers and likes a lumpier idle but I wouldn't go over .500 without other engine mods.