so i'm rebuilding my original 1970 340

You get 22 mpg now, how much more can you possible get and what really $$$$ savings would that get you, what do you spend on gas a year now $500, $1000, $2000? even if you could save 10% on $2000 is only $200 a year. If you do a lot of Highway install an OD tranny but I wouldn't neuter the performance too much for a couple more mpg's.
it's not to save money but to see if it can be done **** i've spent 3000 on gas this summer using vp 110 mixed in with pump gas because of the crap they call gas these days engine would run on when turning it off , might as well piss in the tank gas just sucks