Brush hog

[BrooksAGParts]

It's a World Agritech Corp (International Machine) rotary cutter, appears to be a Model 600H. The gearbox should be a ITG brand 75hp gearbox, 6 spline input and 15 spline output. part number 01-114. If you still need a gearbox I have them available!

 

[Xfaxman]

Big Bee Rotary Cutter is your answer. I don't know much about them other than this is their heavy duty version.
-------------------------------

Yep, pictures online are scarce, but here are two.

Here is a dealer in Tahlequah if you are in the eastern part of the state: 302 Found