Gil, you should peruse some of Big Daves work.
Details: The Red Baron - 2000 Ford F-350 XLT Fuel Economy - EcoModder.com
He has an '00 F-350 XLT 7.3L (4x2) that he has nursed 28mpg out of, and is fairly exacting in his methods as well.
Edit: also note that you can get a clone usb arduino for like $20, it has 6 onboard a/d converters so you can monitor 6 analog signals and send them out the usb port with minimal external circuitry, then figure out the readings on a laptop or ??? And you can get a map sensor from the boneyard for peanuts, stick a thermistor in the airstream and you can compute air mass w/rpm.