You will be spoilt in India for sure - not just for the wildlife but the colours and light too! In terms of distances, it really depends. The guides are very good and will generally stick to the tracks and keep their distance, but you may get lucky where a tiger might cross right in front of the vehicle. In general, though, I would say a 300mm focal length would get you close enough to most wildlife. If you are prepared for carrying the size and weight of the kit you could bring a longer lens, then even better.