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.