Here ya go folks. My cleaned up plans with parts list. It is a easy project to do. The biggest issue with the Curtis controller install was all of the false information, or lack thereof that was floating around regarding the installation. I will post some more pics of my install when i can.
The basics that you need to know is the Alltrax controller was designed as a low cost replacement for the Curtis 1204 series. Both are designed to be used with PM or Series wound motors. This is key to why they work. The Alltrax controls the field natively. The Curtis does not.
The Alltrax will give you field weakening, however you have to sacrifice full motor torque to get it. With the Curtis you can use the original field weakening assembly and maintain full motor torque and have field weakening. It is up to you. There are other apples to oranges differences between the two that i would be happy to answer. There is much background info that i have distilled into this document.
Here is a video of the simple bench setup:
And here she is in the tractor:
V2 - Plans are on the way.