[aerohead]

If you have a university nearby, they may have archived automotive periodicals in the 'stacks' of the library ( ask the librarian ).
HOT ROD Magazine, oddly enough, would be your go-to source for fuel economy articles associated with small-blocks, gearing, fuel management, ignition, exhaust, etc..
* It's possible that, there's a small cfm 4-barrel that will perform as well as EFI, when just loafing down the open road. Small primaries, great atomization, plus 'secondaries' when you really needed power for passing or hill-climbing.
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In Southern California, it was common to use radiator hose to mockup a set of headers. They already have all mandrel bends. Measure, cut, and join with tubing nipples cut from exhaust pipe, up to where the collector would begin.
The sizing is more critical for 'torque' than HP. Hopefully, the HOT ROD articles can help there.
You'll notice that modern Corvettes can close off half of their exhaust with butterfly valves ( borrowed from Hi-Pro motorcycle exhaust ), when they transition between 8-cylinder and 4-cylinder operation. Without the added back-pressure, the engine torque ( and mpg ) would tank.