Need help building 416 Stroker!

Im going to be taking my 1970 340 and building a 416 stroker out of it this winter. Going to be going with a 4 inch cast crank (only looking to make 500 or so horsepower), a set of forged h beam rods and a set of forged pistons .40 over. I have a couple of questions for you guys!

-What kind of block clearance do I have to do for the rod/rod bolts to clear? Is it much?
-What pistons should I use (flat, dome, dish) and what's an acceptable pump gas compression (93 octane used)? (I believe x heads are 72cc chamber)
-The heads I will be using are a set of ported X heads for the time being and then eventually switch to a set of eddy's later on, can these ported X's meet my power goal?
- If I were to go with a flat top piston with valve reliefs, would I have a problem with my valves hitting the pistons with a 282/290 - .520/.540 cam? (stock 1.5 ratio rocker arms)

I believe those are all the questions I have for now guys! Any help is appreciated!