318 or 360?

I want to put together an a body to leave North at our Summer Place in Wyoming. It will be used in the Foothills and the Rockies themselves. If I build a motor for good low-end and mid-range would would a 318 do the job or would it be worth moving up to a 360 and putting up with less mileage


Either one will work and can be built for decent mileage...

My dad had a stock 76 Charger 2 bbl that got 20 MPG, so a 360 can get good economy if built right...