in the 1960s and 1970s most operators moved to lower side band (LSB)
When I started playing on 6.6 in the mid to late 70's it was all AM on either a home made TX & separate RX or ex military kit.
God bless the self oscilator TX which featured in many an EC & broadcasters shack. These TX's with a few minor changes, thats a coil, tuning gang & crystal, would TX from LW to 10 meters.
Amateur (SSB) equipment at that time was massively expensive, even second-hand & virtually impossible to get hold of unless you were licensed, whilst ex WW2 radios were cheap & easy to acquire.
So it was not until what were refered to as "wealthy CB'ers" started emigrating to Echo Charlie in the early 80's that SSB started to become the norm.
Many of the CB'ers on EC were so frightened that unless they knew someone from CB they would not speak to them, yet they would still give massive amounts of information away about themselves during QSO's.
There were several raids as a result of the GPO officers recruiting amateurs to monitor EC bands & note down info like names of local pubs etc. etc. & then slowly piecing together where people lived.
In the 80's with increased activity on Echo Charlie there were even EC rallies held & one at Crystal Palace? I think it was, got raided The 48 meter band was also used for QSO's by a few of the SW broadcasters following thier Sunday Morning broadcasts in the 80's.