Pappy -- Those S-10 5-speeds work okay for the little trucks but I think the guys would advise against using one in anything larger than a 1/2-ton.
To get safely to highway speeds in an AD truck is going to require significant modification to your drivetrain. Several of us are in process of doing that and I'll let the experts tell you about your options. As for me, I am building an AD truck to cruise 65 MPH at about 22k GVW, and to do that, I am upgrading to a 4-53T Detroit diesel, 10-speed Road Ranger RT-610 transmission and a Dana 80 rear axle (with boosted disc brakes). Front axle with be using disc brakes as well and power steering from an International 1-ton.
I don't think there is any way to get highway speeds out of a 2-ton with the 235/250 and the stock rear end, no matter what transmission you use. And the S-10 5-speed isn't enough of a transmission for your application (I think it's barely enough for a 1/2-ton -- those S-10's are actually 1/4-trucks, if I recall correctly).
Hate to be the first of bad news bearers, but you are looking at a significant upgrade to your truck if you want to run highway speeds with it and still carry anything ... AND still be safe.
Grigg is my coach and he is also in Virgina (Lexington area). Where are you? We have a pretty active group of Bolters in the Old Dominion area, so welcome to the Old Dominion Stovebolt Society. Cosmo is our current president.
Regards,
John
