I don't have much info on the conversion aspect itself, but... I did once buy a 164 that had been converted to propane. He offered me the car for $500 complete, or $300 w/o the propane setup. Stupid me, I went for the lower price option.

I did drive it with the propane setup though, and it wasn't very powerful. THen the problem with converting back to gas was that the fella had dramatically milled the cyl head to wicked high compression.... about 13:1 he told me. I could never get it to run right on gas again...

The fellow also told me that it wouldn't run in exremely cold conditions. Somewhere about -10F and there wouldn't be enough pressure to feed the system.

Before I bought it, I also had done some research on the emmissions aspects, and was told that indeed it would pass any normal smog test with flying colors anyday, but that it really wasn't better for the environment... that it sent stuff out teh tailpipe that wasn't detectable by the normal equipment. I don't know how much of that is true though. I was told that natural gas would be much cleaner.

-Matt