In a JD brochure A27-86-10 for loaders, blades, spreaders & snow blowers shows the 856 front dozer blade was recommended for 4640 2WD up to 4850 MFWD, made in 9, 10, & 12 ft. widths with 5x7 torsion tube. The 855 dozer blade was for 4040 to 4450 in same widths but smaller 4x6 torsion tube. 864 12ft. & 865 14ft. blades were for larger 4WD 8430-8850. Don't know of any for sale right now. Might check machinefinder.com or some of the other used online lots. 856 parts catalog should be online also.