Got a question, can a propane system be changed to run natural gas, ex. change oriface like in kitchen appliances? I know that most places in the mountains have L.P. but around cities it is natural gas, could a system be made to make the systems interchangable? Same nozzels but different regulators. Busses work on natural gas why not offroad rigs? Are these engines comletely different technologies?

IIRC there are three types of Propane set ups:
1- Propane Only
2- Dual-Fuel.... Propane or Gasoline
3- Dual Fuel Propane or Natural Gas

on the third set up do you have a link that I can go to for info?

Do a google search for Impco 300.

http://www.propanecarbs.com/impco/300modeldualfuel.html