I am building my first engine ever, I was told by an engine builder that I won't get over 600HP with this combo, but I would like to know two things: 1) is it possible to build a stroker with stock pistons, and 2) what does your magic computer say for HP/TQ?

We'll start at the top and work down
2 Edelbrock 600CFM carbs
Edelbrock C66-O oval port dual carb low rise manifold (not tunnel ram)
Brodix RaceRite Oval port heads (271cc intake, 119cc chamber)
Comp Cams XR270HR hydraulic roller (p/n 01-414-8)
Aluminum roller rockers 1.7:1
GenVI 502 block, 4 bolt main
Eagle stroker crank, 4.25"
Scat 6.385 rods
OE pistons

May be a little more torquey for some of your tastes, but I want something that will be streetable. Are the pistons going to be smacking valves? If not, what kind of compression will I get, and what are my HP/TQ #s?