I asked Dynatrac if they made the free spin for the duellys and this was there Response:
"Thanks for the recent e-mail. Our Dodge kits will work with the 3500DRW. The kit part numbers would be the same, but you would need Spacer Adaptors from Arrow Craft. These Spacer Adaptors will allow my kits to work on the Dual Wheel, Front Axle, application.
Arrow Craft can be reached at #248-280-0210, part #AA-4. Last time I checked they were about $230. 00 for the pair.
I hope this helps, but please let me know if you have any questions. Thanks again!!"
Robert M // Dynatrac Products