Need advice on a 340 stroker engine

Sounds like you've done some reading and have a decent grasp of it. Since you are going to need heads and everything else to get to the 500hp number, the Blueprint stroker engine might be a good option and comes with a nice warranty. You can use TF or will need other decent aluminum heads that flow 275+cfm to give you best chance to hit the number but 550 is harder to get to and still keep mild-ish street manners that it sounds like you want. 450-500 should be achievable with about any aluminum head available these days that has been looked at by a pro. I'll let others comment on the cam but if you really want those numbers, you're going to have to have some lift and duration to get there. Figure .550+" lift and around 235-240 degrees duration for a ballpark. Solid flat tappet makes more power and have less risk with today's lifters. Don't expect a lot of vacuum. Depending on the cam, I think a good single plane intake has a better chance of getting your number on the upper end and the stroker won't give up much torque on the lower end where a dual-plane might be better.
I figured Trick Flow would be great.

My hp goals are just goals. If I get to 500 and it is nice to drive on the street, I will be plenty happy.
I will do some additional reading on the cam. I was not for sure which type I needed. I was planning on also doing a power disc brake conversion kit. Would that affect the type of cam or anything with them being hooked up to the vacuum? The cam is the area I am least knowledgeable so any advice is appreciated.

Any thoughts on the Sniper kit?