While the NV4500 is a great tranny, it has one major drawback, the speedo setup is electronic.
Looking at Lukes suggestion about dropping in a 4.10 pumpkin, I went back and saw that your truck is a 59 model. Luke's right about a pumpkin swap being your easiest and cheapest upgrade. combine the 4.10 gears and tall tires will give you decent rpm's on the highway. I would also go with the SM420 or SM465 tranny, go to
Nowak tranny page for more info on these gearboxes.
Sounds like we both have similar plans for driveline. Mine (hopefully) will have a 292, tranny will be either a SM465 or 700R4, with a 14 bolt rear, gears either 3.42 or 3.73, depending on which tranny I opt for. good luck.
