There is a common misconception that to implement controlled traffic farming (CTF) one must modify or buy all new equipment to begin. In many cases one can trade across or upgrade equipment to match axle and equipment widths over time. That said, with so many makes, models and tire sizes, it seems like every piece of equipment has a different axle and machinery width. 

To simplify your equipment search, I've put together a list of machinery with makes, models, axle widths, equipment widths and tire sizes. I want to thank my trusty intern Nick Moss for his huge contribution to this project. 

Please find the equipment list here which inlcudes tractors, combines, headers, sprayers, grain carts, air carts and even heavy harrows .http://beyondagronomy.com//cmsFiles/documents/document560997bb37e02.pdf

The list is by no means exhaustive but it does include some of the top makes and models for each piece of equipment. I think you'll find this list a very handy tool to get you started in your move to CTF. 

Good luck!

Steve