I can run 60 mph all day long in my '51 burb with the stock rear end, torque tube and '53 235 powerglide engine. Been doing this since I got the truck in 1973.
I would save yourself a whole lot of trouble and just go with what you have. Alternatively you could get the higher ratio gear set from Patrick's for your rear end, and then you could cruise at 65 or 70. Still a whole lot less trouble, and you keep your truck original.
All I carry most of the time is my fiddle, mandolin and tenor banjo.
Kurt
