There is more than one size used on these tractors
1/8" NPT to 1/8" Compression: JJS7403
904 Replaces: BAU2007
VAC series Fits all cylinders with connecting rod # VT3200 or VT4538 and 124
(Jet Star 3 w/ distributor 1112606)
Hydraulic Piston Pump Repair Kit Fits Ford 501 601 650 701 801 Tractors CCPN600A There is more than oneQuality Aftermarket Hydraulic Piston Pump Repair Kit w Plate Assy. & Seal Fits Ford NAA, Jubilee, 501, 541, 600, 601, 611, 620, 621, 630, 640, 641, 650, 651, 660, 661, 671, 681, 700, 740, 741, 771, 800, 801, 811, 821, 840, 850, 851, 860, 861, 871, 881, 90, 951, 971, 981, 2031, 20111, 2131, 4031, 4120, 4131, 2000 4 cylinder, 2120 4 cylinder, 4000 4 cylinder. Some 1953 1964 with piston type hydraulic pump with tapered bearings: Ford Industrial 1801,