1-1/2 Ton Transmission / Overdrive / Gearing Options

[LFEngineering]

So I picked up a parts chassis this past fall to support my 1936 1-1/2 Ton Dump. One of the selling points was the included Warford Auxiliary Transmission. I was really hoping it was going to be an overdrive transmission because my dump truck clocks in at a whopping 40 mph in 4th gear. Well, it wasn't. It was actually a 2:1 under-drive.

I believe my truck and the parts chassis have the optional 6.6:1 rear ends. Making them even slower than the standard 5.14 gearing. Anyone who has seen my custom super single post knows I'm not afraid of fabrication or out of the box thinking.

I would like to make my truck go a little faster, or should I say cruise at a lower RPM. I feel like I'm beating on it driving around at 3500 rpm to keep up with traffic. Not to mention the 7 mpg.

Options:
- Find some mythical overdrive trans?
- Re-Gear rear end to 5.14 gears, that is if I can find some.
- Build some customer adapter and run the Warford 2:1 backwards?
- Build some adapter and run my 2nd 4 speed trans backwards?
- T5? with Open Driveshaft Conversion?

Only Condition is I want to keep using my original rear end housing / axles.

Thoughts?