My son has a SB Dominator on his 318, I'm not impressed with it at all. I would run a stock intake before one of those.
A turbo is a cool idea for mileage but the idea would be to run small cubes (273 again) with the turbo to maximize mileage. Maybe a 273, with 80 318 heads and a turbo off a Cummins. Run a propane system from Pick a Part with a Holley 1850 baseplate.
BTW my kid and I picked up a complete NV 3500 5 speed out of a Dakota along with the hyd clutch, flywheel etc. from pick a part for under $200. No the ratios aren't optimal but it is a cheap way to get into a 5 spoeed that actually bolts up to a small block, his is going behind a 360 into the 240Z project.

Sheldon