My 318 Build with questions

Hey guys:

What I have is a 318 bored 40 over running stock height pistons. I'm putting a Comps cam XE256 in it with a double roller cam set. For heads I have a set of 714's that I had .010 shaved off the surface, the valve increase to 1.88 intakes and 1.6 exhaust and he cleaned up under the bowl and the ports have been enlarged to match the intake which is a Edelbrock performer. I also have a set of TTI headers that will be going on once the cam is broken in. On me the header are on I will be getting the duels with an H or X pipe.

So here are some questions I have. What do you guys think my compression ratio will be with this combo? Thoughts on use a 262 cam over the 256? What do you think this combo will produce in horsepower?

This is my first build and just want to make sure I'm consider everything before I spend money on the wrong thing.

Just for info this is going in a 64 valiant with a 904 push button, right now it has a 7-1/4" with I believe 2:73 gears. Looking for a 8-1/4" 3:23

Thanks for any wisdom
Jon