Any dealer parts place. Use 1 7/16" pins and bush up to I think it is 1 3/4" on the QH to tractor and up to 2" on the implement to QH. Bushings and pins should be common place at the parts house. Cat 3 top link is 1 1/4", not sure what cat4 top link is, but same goes for it. Bushings and pins should be common place at the parts house. I recall reading in the Steiger op manual that there was a cat4 to 3 bushing kit, as it was common to use 3 implements on the 4 tractor.