If you can cut and drill some heavy steel, it is pretty simple to adapt the JD 420/430 model 56 blade, 46 blower, and 47 blower for mounting on a JD 400. Deere once sold a "conversion" kit (nla) consisting of two straps, 3-1/2" by 5/8" bolts and 1-1/2" by 5/8" bolts, and lock nuts seen in the diagram. Two holes are factory-drilled in the sides of the implement frames for attaching the straps. Equivalent straps are readily made from 5/16" by 2" by 9" mild steel flat stock. (I find there is no reason to slot the center hole or to put a notch in the strap). The 3-1/2" bolts take the place of the lower rod found on JD 420/430 implements. Pictures show a strap on one of my JD 420 model 56 blades mounted on a JD 400. Once the straps are bolted on, the blade can be switched between JD 420/430 and JD 400 tractors with no additional tinkering.
Is your JD 420 snowblower a single stage model 46 or a two-stage model 47? The model 47 with added straps will work directly on the JD 400, as the telescoping driveshaft has enough play to accommodate the slightly different pto shaft positions on the two tractors. However, the model 46 will need a driveshaft that is about 1-1/2" shorter if it is to be used on a JD 400. This short driveshaft is no longer available, and there are several threads here about efforts to find or repair the unit.
Harold
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