Why replace it? It's an old technology system, not used much in the first place and not at all now with computer controlled engines. Parts are going to be hard to find locally and if you can't fix what you have you will be down waiting for parts to come from the manufacturer. On the other hand, it's still available, a whole kit is under $600, and spares are available if you want to carry them. It's like a lot of things - older stuff is getting harder to work on.
Alternative would be an air throttle system. Also old tech, far more available, and about as costly to install. I'd probably become an expert in King throttle systems and be prepared to fix my own stuff. Bonus may be that it's usually also a cruise control.
Brian
2005 F250 Supercab, Powerstroke, 5 speed automatic, 3.73 gears.
20 ft race car hauler, Lola T440 Formula Ford, NTM MK4 Sports Racer
1980 MCI MC-5C highway coach conversion
2004 Travelhawk 8' Truck Camper