Your cruise control won't work under 25mph.
I was just thinking, is it possible to modify that, To have it on at any speed? It would be nice to be able to set my cruise at hundred or so RPM faster than my idle speed when wheeling.

Any ideas?

Off to the wiring diagrams!

 

Ya, it's called dual cases...

The crusie control computer uses the speed sensor, not the tach for setting speed. Only thing you could do is fool the cruise control computer into thinking that the truck is going 25 mph all the time (take the speed sensor input and increase the frequency of the pulses to reflect a frequency that is 25mph higher than the input).

Unless you're wheeling on a gravel road, I don't see the benefit of cruise control while wheeling.