timing the same for headers set up? lack power?

timing the same for headers set up? lack power?

Hello, I was wondering what is the timing for a 1973 Plymouth Scamp Slant 6 -225? is the timing the same with Headers or should it be increase?

I was also wonder, is a one barrel sufficient enough for a header set up? or does it need to be converted to a 2 barrel?

I don't want to take away power. when my car didn't have the headers I gotten uses to its power but now since I made a full overhaul on almost everything and it is almost done I was wondering if the one barrel lacks power. I haven't test drive it yet but I have started it to let it warm up and test basic things like lights, Ect... let me know what you guys think. I will post picture of my scamp very soon...