India was clearly an important destination in the cheap traveller boom of the sixties and seventies. Allen Ginsberg's visit which resulted in Indian Journals was in 1962 and he met up with Gary Snyder who recorded his visit in Passage Through India. They were not of course the first.
Overland bus tours were operating from the fifties onwards: perhaps the Indiaman Tour of 1957 was the first. There were many buses on the route in 1972 and I remember the shock I had when I saw a Rotel bus in South India on that trip. I suspect that most of these had drifted to a halt by 1978, as I don't recall seeing overland buses that year, though some were still operating within India and Nepal. The fall of the Shah of Iran in early 1979 saw the end of much overland travel, at least for a while. By then most cheap visitors to India were taking a plane there.
Travellers driving themselves had been doing the trip since the fifties. I remember reading Tim Slessor's book called First Overland written about a Land-Rover trip from London to Singapore in 1955. Nicolas Bouvier, aged 24, did the journey with a friend in an old Fiat in 1953/4, as described in The Way Of The World. All sorts of people were doing this in 1972: I met a retired couple who were driving in an open-top Alfa-Romeo pulling a trailer-tent. Dervla Murphy made her trip by bicycle in 1963, as recorded in Full Tilt. On the way to India in 1972 I saw someone coming back driving a traction engine. The journey was laborious and not difficult if you stuck to the beaten track. People travelling east in a Romany caravan in 1972 were not so fortunate.
I imagine that people were going overland to India using public transport or hitch-hiking from the fifties as well. There was certainly an awakening of interest in the heady days of the late sixties with the Beatles going to Rishikesh, pieces in places like the Whole Earth Catalogue and the first BIT Guide in 1970. Patrick Marnham's book Road to Katmandu gives in its semi-fictional format a view of some of the cheapest of the cheap travellers; his primary trip was in 1968. There were certainly many travellers whose main interest in travelling was drugs or living very cheaply on most of my journeys. Many also found their main experience of travelling one of dealing with hassle and misfortune. But there were many others as well.