In 1990 I converted a 302 1973 Bronco to straight propane. Got rid of the carb altogether and it was replaced by a 'mixer' which essentially does the same job as a carb. There is also a device called a vaporizer which converts liquid propane from the tank to gaseous form and it is like a pressure reducer too. Vaporizer goes between the tank and the mixer, usually very close to the mixer. There was also a safety device called a lock-off valve which would stop the flow of propane altogether unless there was some manifold vacuum. That went just before the vaporizer. I put the tank between the back seat and the tailgate.

I drove the Bronco on propane for 11 years (daily driver) and loved it. Here in BC you can get propane at many gas stations so that isn't an issue, plus it is about 2/3rds the price of gas. The truck would just fire right up and purr like a kitten even in icy cold weather; with a gaseous fuel no need for a choke. On a vehicle of that age with a carb to begin with, going to propane is definitely an upgrade. Oh ya - I did recurve the distributor as propane likes the advance to come in differently than gasoline.

The only downside is propane powered vehicles tend to eat exhaust valve seats so you need to install hardened exhaust valve seats which solves that problem. That and a tiny reduction in full throttle power but the better driveability and cheap fuel more than made up for the slight HP loss.

I also converted my 1967 390 CID mustang. With 10.5 to 1 factory compression ratio it didn't really like modern pump gas but propane is good to 11 or 11.5 to 1 without pre-ignition so that helped me decide to convert the mustang. That plus the very positive experience of driving the Bronco on propane for all those years. The mustang might not have been quite as quick in the 1/4 mile on propane but for general driving it was so over-powered anyhow I couldn't notice any difference.

I am looking for an F 250 4x4 right now and hoping to find one already on propane, actually going to check out a '94 F250 next week. Hopefully it will be good and I will end up getting it.

Not sure of the price of propane in the states compared to gas. Is it similar to here where propane is 2/3rds the price of gas? Also, availability... can you get it pretty much everywhere like here in BC, Canada?