John E
1. go to their web site cascorp.com, click the attachments tab, click on custom products check them out. There are others the make these attachments - do a bit of googling to see what other options are available to you. Cascade is a good reputable company been around a long time.
2. suggest you contact others in your same business & get some advise.
3. Call the tire supplier & ask them what they use to load the tires out on the trailer.
4. Pallets for tires due to the variety of OD's would be custom sizes and your freight/handling costs would go up and be reflected in the product cost or shipping costs and over the road charges as pallets take up space inside a trailer.