Just a couple thoughts on your carburetion:
The inline engines have always had issues with fuel distribution due to the length of the engine. (I owned straight-eight Packards, where it was even worse.) With a single carburetor in the middle, there is almost always more fuel going to the middle cylinders than to the end cylinders.
This hurts fuel economy because getting enough fuel to the end cylinders to prevent an over-lean condition results in excess (wasted) fuel supplied to the middle. When you "punch it" and the accelerator pump sprays raw gas into the intake, this situation is briefly even more pronounced. From a standpoint of both optimal power and best economy, you want each cylinder supplied with only as much or as little gas as it needs for the momentary demand on the engine.
There are multiple-carb intakes available for this engine, which would help considerably. If you find a setup for dual Webber 36/38 carbs, be aware that these carbs were used on some Pintos and other 4-cylinder engines, can be often be found used at a reasonable price, and rebuild easily. Barring that, if you use only a single carb it could possibly be an advantage to use a small (465 cfm?) vacuum-secondary four-barrel rather than a large two-barrel. On low demand, the four-barrel is using only the small, primary side of the carb, while the 2-barrel is always using the entire carb. Operating at a lower flow rate due to the larger cross-section, some two barrels are not as precise at metering fuel based on venturi-effect vacuum signal.
If you have room, maybe you could look into fuel injection, as used by Ford on later engines. I know fuel injection can sound scary and like a trip to the unknown, but if you do a quick read on how it works, it really is very straight-forward. If you have U-Pull-It yards, or check CraigsList, the complete stock setup may not be prohibitively expensive. It would sure give you better performance potential on both the power and economy sides.
Of course, this leads to thoughts of a way-cool-sounding dual exhaust!