An old timer (who was present at a private screening) once told me that in the "original" ending of the movie, Gabbar (Amjad Khan) rolls off the boulders and lands on iron rod(s) when kicked by Thakur (Sanjeev Kumar). He is impaled on them or is seriously injured, leading to his death.
However, this ending was considered too soft and didn't exactly give a meaningful conclusion to what was supposed to be a revenge saga. Moreover, the producers thought that this ending will not stir the emotions of the audience as the ending was too, well chancey!
This led to Ramesh Sippy shooting the next version in which Thakur kills Gabbar. And then there is the censored alternate version, mentioned in Wikipedia.
Hence,
Total count of different endings = 3