stupid long or shorter headers?

[WSSix]

Should be a 500hp 383 if I get the supporting mods correct. The company that's doing the heads and suggesting the cam said cars are typically in the 420-440rwhp range with the setup I'm going with. The heads flow just under 200cfm max on the exhaust side. I'm looking to redline at 63-6500. All my math tells me I need 1-3/4" headers. While I'm not trying to build a race car, I don't mind trying to do it as best I can so that I can hopefully surprise people that usually look upon LT1s as junk.

Thanks everyone.