Streetmaster 318 vs. Performer for street use

Is it worth it to remove the street master and get a street dominator?
I've already got the street master on there. And it seems to do ok. My carb set up is crazy but I'm going to a Holley 600 for my 318.

Otherwise it's a stock 1976 318.
I was looking for fuel economy.....it has a points distributor and stock everything else. I'd like to get over 20mpg in my 69 dart.