The Indian Air Force has (or had) atleast 2 ex Air-India 707s modified into special mission aircraft. They were used by the aviation wing of the Indian intelligence agency RAW. They have RC-135 like side looking radars and SIGINT gathering equipment. Not sure about the landing gear overhaul though.
These 707s will probably be replaced by newly procured Global 5000 based SIGINT platforms.
Edit: Israel did the job of modifying those 707s and the Global 5000s.