250 3ott 3:08 combo

[68panelman]

Like title says. Anyone running this drivetrain? My has 67 has all but with a 4:11 rear, 28" tires, stays happy at 60, looking for more and better gas mileage
Found a 3ott overdrive somewhat local, but then a shortened driveshaft comes into play, but I like the idea. A 5 spd will definitely be the most expensive route but I enjoy column shifting too much and don't want to cut my floor. Anyone have one of the combos for info?

Thanks, Mike