I hate to spend money! I've taken some flack over my cruise control idea because of the obvious safety concerns.
I plan to use a hand throttle. It was designed for use on a fire truck to control the speed of the engine thus governing the amt of pressure the pump puts on the hoseline.
The throttle can be closed two different ways. it's threaded, so it can be turned a few rounds back to idle. There is also a big red button in the center of the hand throttle, when pushed, it returns the engine to idle.
I know this is not the safest method for cruise control, but it seems realatively safe. If it got stuck or developed a problem, one could always turn off the engine. My brakes have more clamping power than the engine does pulling power, so the bus would stop if some unforseen problem arose. Although it would take significantly longer to stop the bus if the engine is turning a lot of rpm's.
Unless i run across a simple cheap diesel cruise control kit, I think the hand throttle is the direction i'm going to take.
Quis custodiet ipsos custodes (who will watch the watchmen?)