350 Timing?

[PhoenixRising01]

I have a '71 c10 lb. Recently replaced motor with a crate 350. After a couple thousand miles had a mild cam installed. I didn't get the performance boost I wanted. My question: What is standard timing, and given the cam, what would be a reasonable amount of advance? People I've asked have suggested I take it up to 30 degrees after tdc. I'm pretty sure that's way too extreme.
Another question relates to replacing stock exhaust manifolds with headers. Is there a real world advantage to this? I'm trying to get the most I can out of it without boring, new heads, etc. Thanks for your help.