I don't think you're going to see anything major. I'd suspect probably a 1-2 MPG increase, maybe. There would be a fair amount of work and mods, but is there anything on a Jeep that isn't?
It'd be great for the wow factor though.....Just don't see too many inlines with a 4 barrel carb.
My last inline 6 was a 250 Chevy and with most of the things I did to it, I never did any modifications to the fuel system above a later 2 barrel. With that and an HEI, it was pretty strong, but would top out at about 4,000 RPM max, and I don't recall the fuel mileage at the time. Wasn't great with 4.10's and a Saginaw 4 speed though.
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