Daily Driver Engine 318 vs 360, what one?

I think N/A your best bet would be to use a 360 roller block and stroke it out to 408. Custom cam grind might be a good idea for best mpgs.

I think the best way to achieve your hp goals and good mpg would be a turbocharger. Get a 318 roller block, beef up the internals, again a custom ground cam might be a good idea here. Slap on an apropriate turbocharger with a good fuel injection setup. Its not cheap but would work very well.