I worked at a Allis dealer YEARS ago. Normally Allis engines set-up for LP had a higher compression ratio sleeve kit than a gasoline engine. I know there were factory LP WD-45's. Check the brand of the LP carb. and evaporator/demand regulator. If they a ENSIGN brand, now defunct, it is original factory set-up. I have a C-II Gleaner with a G-262 Power unit that is LP and I almost bought a Gleaner Model A that was LP. I with I could find a usable set of LP pistons for a ALLIS G-230 power unit. The LP piston were also sometimes call High Altitude pistons.