I almost did this myself - bought a Ford E150 conversion van with wheelchair lift at a Goodwill auction and got it running. The lift is pretty capable but its only an inch or two wider than an average wheelchair, so a 40" pallet would be too wide.

In the end I didn't like that particular van very much and just sold it. You'd be surprised at the demand for reasonably priced wheel chair vans. Some guy drove up from TN just to get it for his grandson. It didn't even run that well.