So the question is, does the van have the HO56 rear axle, and if it does is the gear in it a 4.10 or 4.56 or 5.13 (3.90 and 6.17 are scarce as hens teeth or mythical).
Does the yard guy have access to the internet? If so, ask him if the axle looks like this one (picture 8 on link)
http://www.blackbirdscustomtrucks.com/index5.html If it does, then get that 3'rd. I got my 4.10 already to replace my 5.13.
