Hey Aaron,
IIRC, in the early days (months?) of the Tape Project forum, Mike Paschetto (Mikey on this forum) had JFR switch out the heads of his Technics to some 400mH Tascam heads which he found to be more "tube friendly".
When you contact John French, you might ask about that. I would guess that if he was able to get those heads into the Technics headblock, getting one into an Otari with and outboard tube pre should work (maybe John is assuming you're using the stock playback electronics?).
Just went back and took a gander at the post I was referring to and I was wrong-wrong-wrong!
Here's what he actually got,..
1/4 track playback head, Panasonic RPB-065 (560mHy, 400 ohm DCR)