Turbo slant would be a much better option, way less weight, just over half the capacity.
If your truly after MPG, then have a bit of a look at ecomodder.com and the mega weight loss thread here
https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2255190/1.htmlAero and weight, plus a well tuned engine is about the extent of achievable stuff without spending stupid money that could just be spent on fuel, especially if its not a daily driver
That said, this one popped up in my feed the other day, lawnmower carb on a ford 302 that gets 40mpg, so the dude claims
https://www.youtube.com/watch?v=1xHQWu2ZzPc
