Khardung La
I did the Khardung La thing in 2011 for my 50th birthday with the Enduro Himalaya lot. Shimla to Leh in 2 weeks then up to Khardung La. Quite expensive with E.H. but the backup is impressive. I highly recommend the trip whoever you do it with.
I also did Karnataka and Rajasthan back in the late 90s. Go to Jisalmer, Ranakphur and Hampi(Vijayanagara). You won't regret it.
Steve.