LPG (propane) conversions are very popular in Europe.
You get basically a second fuel system installed with a propane tank instead of the spare wheel under the truck. You can still drive on gas and switch to propane. MPGs are usually 20-30% less, but with the gas prices where they are now you still save 30+% in money.
'97 Blazer LT 4x4 L35, G80 one of 62 Euro specs built & shipped to Germany in '97
'98 Blazer LT 4x4 L35, G80