How fast will your truck actually go?
I have a 1950 216, 3spd, 4:11 rear end and I have no problem reaching 65mph. I can cruise on the interstate comfortably at 55-60 without undue stress on the engine.
When the truck came to me the owner said he couldn't go faster than 30mph and blamed it on the "low gearing." Of course it turned out that the clutch was slipping badly at about 30 mph and on any hill.
It also had crappy 15" wheels on it with tires of too small diameter. They were also too wide. You could barely steer it.
Installing a new clutch and original size 16" wheels an large diameter tires made getting up to 60mph easy as pie.
If your truck can't reach 55-65mph, you have problems other than a low geared rear end.
