Never too old to learn--just looking at tractordata.com, I see three compression ratios listed for the WD45 226 engine. The common gas, a lower ratio for "tractor fuel"(I suppose the true dual fuel-start on gas run on distillate) and a higher ratio for the LP model. I assumed the gas tank was just used on the WD45 LP as a dummy to hold the hood. Probably cheaper than coming up with something else.
Used to be lots of WD45's around. No LP's here. Very few diesels.