Ive run lpg for years on various cars from 3cyl 2 stroke susuki 4wd holden 6cyl landys, turbo 13b rotary mazda rx7, and my HZ 253 prem wagon.
There are good reasons to run lpg but for me the bottom line is $$$$$. Here in WA the price of gas has risen to the point where gas is not economical.
It was acceptable when lpg was 50% the price of petrol . But now its as high as 85% and in my experience can cost moor per k.
Yes it is a better fuel if the engine is properly built for it (high comp ignition re map cam good intake good exhaust etc etc).
Lpg like petrol is sold by volume and from memory lpg is 15% less dense than petrol and has a lower calorific value as well.
So when you buy 100l of petrol you would need to buy over 115l of lpg. and when you factor in all the other losses incurred when running a gas system on an older carby vehicle .For me gas is no longer a viable option.
Cheers Nathan