Street performance tips, 225 slant 6

I just got my first mopar, with the 225 slant 6.
Its a Dodge Dart custom 4 door, from 73.

The motor is orginal, but i want some more power out of the slant.

I was thinking about getting a 4 barrel intake and some headers, maybe a performance camshaft, but most likely Il wait with the cam.

Ive looked around on the net, searching after tips etc., but cant find very much abaout the carburator size.

So I was hoping somebody in here got some knowledge about what works best in the street, with toughs of mpg vs. performance, like wich headers, and intake (2\4 barrel) works with what.

I live in norway and we have to pay about 2 bucks for òne litre of gasoline, so mpg is pretty important!

btw. When i start up my dart, and the engine is cold, the choke works, but when i give it a little gas, it dies out. Even while i drive it, if I let go of the gas pedal. Does somebody know what this might be?

Thanks!

-Po