There's big and then there's bigger.
19 teeth on that pinion? Is that Felony's 2.47 pinion gear? If so, his '72 Gran Sport must be the size of a star ship and his 521 must be measured in cubic feet!
While you were taking drugs first thing in the morning (not that there's anything wrong with that), I was being nagged by the Ghost of Parts Purchases Past about my speedometer info. So I dragged it out of the vault to verify. Yep, drug abuse can skew memory. Who knew? This a 140-mph police unit stamped "Calibration Certified" in the face, with a Dec 20, '72 date stamp on back. Also a "J"; maybe a revision or assembly code number. It is not NOS, showing 50,583 miles. I'm sure I have another speedo that is NOS in the vault, but it is not this model.
Both the '72 N-code 429 Torino GS and the '73 N-code Montego GT have 2.79 gears from the factory. The '79 Ranchero GT really does have 2.47's, people. Please check the bottom of the first column here:
https://www.supermotors.net/registry/media/419687_1 Note also that there is a 2.26 ratio option (G-code). That should feed you pinion strokers for days to come.
We've all seen these "street race" videos that are actually highway blasts from a 60 mph roll. I gotta imagine how a 500+ incher with these type of ratios would stack up in that scenario. Anyone here have a freeway flyer?