I would be surprised if you star wars air cleaner would fit.
With typical driving for 1000 miles a year at 15 mpg is about 67 gallons per year. If you got a 20% increase, you would save about 13 gallons of gas... Not much payback.
I find most people complaining about mpg have ignition issues which a good tune up shop can fix. ( or if you are keen on fixin' things you can too ). And, as soon as ignition is mentioned, everyone want pointless HEIs. I am not a real strong supporter of that either, the main benefit being a hotter spark, which you can get with a high performance coil and points ( for restoration you can take that red/yellow/chrome coil and paint it black and no-one even notices its there ).
Sorry, maybe the next reply will be more supporting