Hi Mark,
You've got good advice and indeed the stylus for 78s is quite a bit larger. If you used the much smaller styus for 33 1/3 or 45 rpm "microgrooves" (as they were first called) for 78s, it would ride down in the bottom of the groove, picking up all kinds of groove noise and garbage. I'm away from my archives at the moment, so I can't specify the tip diameter for a proper 78 stylus, but check on Shure's web site. They continued to supply specialty styli for years. So does Stanton, which has a big broadcast market (or did in the past). I think Stanton might even have a direct-drive turntable with a 78-speed option but I could be wrong.
Regards,
