This is the beginning of the Hustler ID list. If anybody has the years of the model produced, axle diameter or any other info/changes please let me know. There may be mistakes here at first please let me know. I will edit this as we go. Here is a start I found from an older thread posted by Jpswift1. Thanks to all that help here.
Here is another thread you may be able to use to help ID your year. If you have a known model and year could you please post it.
Year ID
19xx Hustler (unknown model number), fiberglass body, Kohler 309cc single, jackshaft/clutch style transmission, formed body for jet pump option.
19xx Hustler 880, fiberglass body, CCW twin engine, T-20, formed body for jet pump option. 6 chain frame. 1" pinned axles with 5 bolt flanges welded on,no gusseting. 47mm spherical inner brg's. 52mm spherical outer brg's in 3 bolt triangular bolt pattern. No split shifting. Parking brake on left mid axle. Metal fuel tank
19xx Hustler 900, poly body, Kohler 440cc twin engine, T-20
19xx Hustler 945hk, Kohler k341
19xx Hustler 950, poly body, Kohler K341 single 16HP, and 18HP 694cc Briggs I/C twin engines, T-20.
19xx Hustler 980 BIGFOOT, tall and very tall lower bodies, 18HP 694cc Briggs I/C twin engine, T-20.
19xx Last year of production and models xxxx