I've flown as pax on almost all of the double bogey birds, except the one that crashed in BLR. As crappy as AI hard product can be, it always made me happy to see one of these birds waiting at the gate for me. As an aside, I think the NEO would look even more like a cool little widebody mini-me if it had the double bogeys - imagine!
The older birds with the double bogies were refurbished with all new seats during their D-check in 2010 time frame. The interior layout was also changed to single class 168Y at this time. Pretty decent interiors. The only problems with the old birds was frequent problems with AC packs.
Air India also did this with some B727's so they could land on unimproved runways. Years ago I worked for a company that Bought them for spare parts.
The Gear Legs could be converted for the Highest GWT B727's with the Dual Wheels which were already Freighters
Air India and Indian Airlines have NEVER operated the B727's. The only time 727's showed up on Indian Airlines timetables was as codeshares on Aghan Ariana and Royal Nepal flights. For a brief while in the late 80's, 727's of Royal Nepal were used for low-fare night flights on DEL-NAG-BLR and CCU-NAG-BOM flights which showed up with IC/VD codes on timetables.
PS: I swear I saw a double bogie A320 in Raipur in XMas week when I was in India. Couldn't catch the reg, but it was there at the time AI's DEL-NAG-RPR flight operates.