Good Morning,
I have managed to buy a TK60 head from Germany, once it arrives i will see if it works in the TK64. But for now, it works well,
Playback in Stereo is great, from tapes and the turntable
Record is great, but with the switch in mono. Sound is excellent, loud and clear. Must have been something in 1962
I made a youtube video of it recording and playback in Mono.
https://www.youtube.com/watch?v=DDNKTguzkuk
Hope you like watching