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An 83 should also be a 351W, it came in mid year 82, but, there may have been an carryover, Ford has been known to do odd things...
Best I can do for you is specs for an 81,
For the M, and the 300, the lower set of numbers is below 8500 GVWR, higher is above(F250HD/F350)
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Slideshow: The VelociRaptor Expedition gains a lift, upgraded suspension, Brembo brakes, and trail-ready equipment while retaining the stock 440-horsepower EcoBoost V6.
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Slideshow: Called the Fortress, the 850-horsepower pickup combines Raptor underpinnings with military-inspired features, survival equipment, and a starting price of $285,000.