Hi lawngrub, welcome to Outdoorking.

That seems to be quite an early Greenfield, possibly made soon after the first model, the HD8, which had a horizontal-crankshaft engine. Yours, having a vertical crankshaft, probably has much the same basic design as the various long-shaft models that followed, up until the short shaft was introduced. Hence its parts are probably fairly similar to the Tractor 5, 8, 10 and 11 - in fact most of them are likely to be the same parts. However to get a closer reading on the actual age of your machine, we need the Model, Type and Code numbers for that 8 hp Briggs engine. These numbers are stamped on the cooling air cowl, though they may be hidden behind the fuel tank on yours, on the vertical surface of the cowl shown by the red oval:
[Linked Image]

If you post that information, we can try to locate the Illustrated Parts List and Operator's Manual for the engine. We can also locate the overhaul information for the engine.