PTO Motors
Thy PTO hydraulic motors from Surplus Center - http://www.surpluscenter.com/Hydraulics/Hydraulic-Motors/Ag-PTO-Output-Hydraulic-Motors/ are these:
http://www.dynamicfc.com/documents/BMSY.pdf
These are Dynamic Fluid Components BMSY series, and the PTO shaft is one of the shaft options.
File:DFC BMSYptomotorspecs.pdf
The 5 cu in one is the BMSY-80, and the 10 cu in is the BMSY-160.