Larger tires do wonders for higher speeds!!
Use this calculator
http://www.onlineconversion.com/bigger_tires.htm
In the "find MPH" plug in 2500 rpm, 5.14 axle ratio, 1 for the other ratios... then see the MPH difference between 28" tires and 33" tires, about 7 mph.

On an AD 1 ton about as big as you can fit is 32" to 33" depending on width and the condition of your springs. I ran some 8x19.5 and 8R19.5 tires on my 52 1 ton, they just fit and looked great.

Switching to 10 lugs is not necessary to do that, 8 lug 19.5" wheels either single or dual are available.

However, I did switch to 10 lugs on my 1 ton, the small GM 10 lug on 7.25" bolt circle, and ran the GM dual type 19.5" wheels on front, custom wheels on the rear.
That was just an intermediate step in my truck projects and now the same axles are under my 2 ton, this time with 22.5" wheels..

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-