I already have a 66 two ton that is on the road all the stock running gear is the same as my 56 it now has a mildly built 350 in front of the SM420 that came from the 56. I blew the rear end up and it now has the center section from my 57 parts truck in it. With the SM420 and 10.00R X 22.5 tires which are taller than stock it will cruse at 55 and can make sort spurts to 60. If you used an NV4500 you would have overdrive that would make 60 a high cruse but bearable that is if you also switched to the larger tires. The tire swap from 8.25 x 20s to 10.00R x 22.5 made all the difference in the world the truck had good tires on it before and drove nice but the bigger radials made improvements I would not have thought possible, both in top speed gearing and drivability. I use the 64 to pull a 12 ton equipment trailer and a 14,000 lds mini excavator the whole rig weighing in at 26,000 and every thing has worked out great. keep in mind that all brakes truck and trailer are keep in tip top shape and the rig has the ability to put you though the windshield in a panic stop. This truck dives great handles and stops very well it is however old and requires attention to detail when it comes to maintenance. Keep it safe and start with all new brake system if you keep it stock it must at least be completely rebuilt.
I do have to agree with Grigg though. If I had it to do all over I would have found a late model Top Kick with a diesel and bigger transmission more GVW and swapped cabs for the classic look in a new truck.
