I had one grain truck that ran on LP. It was a Chev C-65 with a 366, GVW of 48,000 (and typically run at that weight) and it was a full LP conversion rather than dual fuel.
The economy on the truck was the same (cost of fuel + lowered mileage + road tax that needed to be paid annually since it wasn't included in the fuel price = no advantage or disadvantage economically). Drivability was fine with no discernable power difference. With 25,000 of tank space (20,000 real fill limit) on the yard, and plenty of fill stations for the 20 lb tanks around filling up was no problem. I had two tanks set up to fill - one on a hog barn next to our gas and diesel tanks, and I had a fill hose on one of our dryer tanks so I could fill the truck while unloading at the bin site.
With all that neutral there was a downside. Here in the great white north it had a starting issue. Many lp vehicles are actually dual fuel, so you can start on gas and switch to lp once they are warmed up and capable of vaporizing the fuel. Whenever the temps dropped below 30 F I had to plug the truck in to get enough warmth in the coolant to vaporize the lp. Even with the truck plugged in, on cold days it would take several miles to get enough engine heat to produce full power. Remembering to fill out the log books, file the paperwork and pay that full year of road tax once a year was also a pain ... But not as big a pain as being 300 miles from home and explaining to the gal at the station that this is just like filling those little bbq tanks except you watch the gauge instead of the scale.