The Bolens 900 (model #189) was a model produced for 1964 & 1965.
It had an 8-1/4hp Wisconsin engine, and was equipped with a 3-speed transmission, however the tractor had effectively 6 speeds. ....There was lever to change from High range to Low range by moving an idler pulley from one engine drive belt to the other.
The Bolens 1000 (model #190) was 1965 only.
It had a 10hp Wisconsin engine, and a 6-speed transmission. ....The High-Low range change was done inside the transaxle.
There were other differences, but these were the two most prominent.
Bolens never released production figures to dealers, so I don't think you will ever learn how many were actually made.