LP gas (Propane/Butane mixture) is approximately 110 Octane. That's a good thing- - - -you can bump the compression way up (12:1 or so) without detonating IF you can find the right pistons. Don't even think about milling the heads- - - -they're virtually flat, and the "combustion chamber" is actually in the top of the cylinder with that oddball angle between the top of the block and the cylinder.

Downside- - - -LP displaces a lot of volume of air as it mixes with the air when it goes through the throttle body. That reduces the horsepower you'll get on gasoline by about 10% or more. LP is also rough on exhaust valve seats. You need Stellite hard seats on the exhaust valves if you ever intend to use the truck like a truck. If you're just tooling around in "Cowboy Cadillac" mode, you probably don't need hardened valve seats.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!