For the WS-AP3805e, running 10.11.01 firmware, I see channels 36-64 available for India. This is with the small PRO-ANT-DIP model antennas connected. As Zdenek and others have mentioned, the available channels can vary depending on antennas as well as other factors.
This kb article explains a more on the variables taken into account with compliance testing.
Available channels can vary due to antenna, channel width and also between models, different firmware versions, antennas, etc.
I have seen other AP's that have some of the upper band UNII-3 channels (149-165) available in India, but not the AP3805i model.
That being said, with a large deployment like you have, I agree with what Philipp has commented. It is fine to use 20mhz setting with 5ghz and very much recommended.