Finally decided on a cam for teen SB. Should I bother with header?

Headers, buy Dougs D-453. ~500 at autozone for coated using a discount code.

Valve springs could be an issue with it cutting off.

Ignition, what RPM did you stop to get the total number? You must run the engine up until it stops advancing. Many say go to 2500-3000 and see what you have, which may be wrong. Lots of mopar distributors don't stop advancing until 4K or more. Sounds like it may be detonating.

Fuel, or lack of, would be another area to investigate.