Do you know what the rear end gearing is? If it has really "short" gears (3.73, 4.10, etc.) and no OD, then highway cruising is going to be a challenge. There may be a metal tag on rear axle or pumpkin with gear ratio stamped on it, or you can manually spin rear tires with vehicle jacked up and count revolutions of drive shaft and tires. In short, "short" gears were not meant for today's highway speeds, they were meant for heavy load hauling. If you want to make this tuck more of a cruiser find a tranny with an OD or swap out rear end gears for something "taller" like 2.73 (just don't expect the same jack rabbit start with those gears tho.)
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