Similar set up in my GTO,a 406 w/Crower 60242 (similar to your 60916).
I switched from 3.23's to 3.90's this year. It pretty much rendered my street tires useless below 20 MPH. I went from a Goodyear 255/60/15 to a 10.5/27/15 MT ET Street to be able to get any traction. 60' times at the track dropped .3 of a second. Anyway,yes ,it made a nice difference with the gear change as far as acceleration. I too almost never drive on the highway. Any driving above 60 MPH is annoying.
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‘63 LeMans- ‘69 400 w/ original transaxle. 2.69 gears.
‘55 Catalina
‘62 Mercury Meteor-all original, bought new by my grandfather
71' GTO -original 400/4-speed/3.23 posi
13.95 @ 102.1 on street tires @ 4055lbs.-now my sons ride
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