Hi  Richard,

I looked on eBay for Roundhouse SP ore cars, as that's where I thought the MDC trucks were used, but the photos in the auctions I found were not conclusive.

Have you seen Cory Bonsall's trucks used under the Utah Coal Route 70t gons?  Here's a link to his auction for them with pretty good photos:

https://www.ebay.com/itm/HO-Scale-3D-Printed-Truckframes-70-Ton-Carbon-County-Railway-CBC-2-Pair/232519243454?hash=item36233a16be:g:GwIAAOSweIlZZrgX

Todd Sullivan