What do you exactly mean by "you need to replace the hub pulley"?
Why do you need to replace it?
If you are having problems with spline wear and knock you will need to replace both the shaft and the drive hub.
That is no piece of cake...lol
Don"t know where you are but I"ve got a 300 gas in very good shape, serial number in the 19000 range w/ a 13" bean head (love bar), and a 222 corn head. The corn head hasn"t been used in a a few years but has been on a cement pad and is still in good shape.
We don"t use the 300 anymore anymore and it"s just too good a combine to let sit out and rust.
The combine and cutting head have always been stored inside.
I"m located in SE South Dakota and can send pics if you are interested.