New bb build fuel economy

Hi like your way of thinking,what cam did you put in,specs ? This build is still on the drawing board and im gona start saving up parts soon,just want to get it sort of right from the start,im going whid the stock 400 cui and close chamber iron heads,got a buddy whid a full service head shop and he makes 5 angle valve Jobs for nothing so im covered in that part of the build,I always belived in high comp and low friction so im going thath route

How much driving do you plan on doing, what mileage does it get now, what does that cost ??