heh-heh
Boy are
you a newbie!
I don't know if I'd want
any engine bored .080 over. Too much potential for disaster. An .080 overbore usually means at least two previous rebuilds. Those cylinder walls should be examined
closely if you choose to proceed.
Sounds like you have a reasonable dream - decent power and fuel efficiency. I hope you realize the cost of bringing that dream alive - $$$$$.
One last thing - it's difficult to give you an mpg figure without knowing what kind of '55 vehicle the engine is going in (car/truck?) and what your final drive ratio will be. And then it will be a guesstimate.
