I have not been able to locate any sources for the body-to-frame mounts for the Econoline. I was referred to Energy Suspension, though I do not find any listing on their site. I'll probably give them a call to verify tomorrow. Otherwise, would mounts from a truck be similar enough?
Check with your local wheelchair van conversion center. They will have all the info you are looking for. They lift them 3 inches to drop the floor three inches so people can driver from their wheelchairs with out getting into a seat to drive.