My Pony clamps are between 20 and 40 years old and are 3/4NPT. I would believe the ones sold now are the same but you should ask the seller to confirm. You can also buy an import hand threader and thread the pipes yourself.
Galvanized pipe is reputed to slip a little more but I never noticed on the few I have. They are also supposed to wear the edges of the clutches but you can flip them around for more life. I have never done that. The advantage to galvanized pipe is that should the pipe touch the wood and glue it won't turn the wood black, like black iron pipes do. Put a bit of tape, paper or space the clamp off the wood with a little strip of wood 3mm or thicker....or don't be sloppy with the glue.
https://www.amazon.ca/Threader-Plum...=hand+pipe+threading+set,aps,237&sr=8-10&th=1
Pete