Be sure your tire size is maximized for a slight top end assist. If running modern 13" tires, the profiles are typically much smaller diameter?circumference. 14" wheels with '70' series tires will lower cruise RPM a bit if absolute originality is flexible.
Other mods require more work: Swapping an Overdrive transmission is the best alternative. . Automatic OD's are outside my data base. 80's Mustang T5 manual is a favorite for early cars, again if absolute originality is flexible.
Maverick and rare early Mustang 8" rear ends with higher ratio's will
semi-bolt right in . Rear end gearing can dramatically change cruise RPM but with 170/2Spd Fordomatic may have poorer
drive-ability result.
'63 More-Door Wagon
C8DE Ford 170, Precision Machined D7 Head . Oversize intake valves/1.50 exh with- silicon springs and HD retainers, . Milled head w/ Steel Shim Gasket. CR= 9.5:1. H/W 5200 - 2.8 series (32/36) progressive 2Bbl carb., Exhaust ¾ siamese port divider, Champion racing spark plugs, Contact Point/Condensor distributor, Diaphragm Clutch. T5 Adaptor/5speed tranny, Short throw Hurst Indy shifter, OEM 3.50: rear, Shelby sway bar, Addco rear sway bar , Fabricated subframe connectors / crossmember, Hooker 6601 dual out longtube headers. Shoulder belts front and belts for three in rear, Dual chamber master cylinder, OEM wide-wagon brakes, dual air line rear shocks, 14” wheels & 205/195-14 tires, Countersprung Tailgate, Original tube radio …