Yes, all the stats are bassed off real measurments. The larger wagons are a bit larger than was typical in real life, normally not exceeding sets of rows of 2 horses, and prefering a train of wagons divided between smaller teams rather than one giant one. But giant wagons and/or teams of more than 2 animals wide were used for things that couldnt be taken appart, or by people who wanted to flaunt their wealth, or as experiments while developing better technology and methods. I bassed the handcarts off what Mormon pioneers used when they were trecking to Utah, as they keet very detailed records about those, even doing miniature or full reinactments of the trecks for the youth who wish to try experiencing it.
The one place I didnt go to real life was the pricing, as those were FAR more varried than the actual carts and wagons. I went to the Arms and Armament book from 3.5e for general pricing references.
Oh, speeking of pricing, everything is currently measured as per the normal gold standard, copper-platinum. It's easier for me to concieve and compile these on that standard. When I completely finish a doc, I'll make a full conversion to the Farland silver standard.