timing the same for headers set up? lack power?

No engine needs backpressure (backpressure is pressure that builds up in the exhaust system). ANY energy used to push exhaust out is energy that can't be used to turn the tires. Headers commonly scavenge enough better on a low performance engine to cause it to run lean with the factory carb. Or, to put it another way, you are now moving enough more air through the engine that the carb can't flow enough gas to keep up.

Is a 1bbl sufficient for the header setup? With a larger main jet, perhaps, but it will be your limiting factor. It sounds like you have plenty of exhaust system now. Your car would certainly run better with a 2bbl or perhaps even a small 4bbl. This would mean a manifold change including linkages..

As for timing, experiment with advancing it. Start out at 5 degrees BTDC or so. Whatever the middle timing mark is. Test drive. Now advance to the outer timing mark. Test drive. Is it better? If so, advance by that much again, moving the mark off scale by the same amount you advanced it last time (like 3/8 inch or so). Better? Do it again. Worse? Go back and home in on the best setting. You can probably run 10-15 degrees initial in a slant with no problem. Obviously, if it starts pinging, your are at the limit of advance.