I have a 1989 GT Karakoram with an unusual 1" threaded headset. Both upper and lower races and cups are inverted. I mean the bottom cup is pressed onto the fork crown, the lower race is in the bottom of the headtube and the top cup is pressed in the top of the headtube. The upper race threads down the steerer tube.
It needs replacing though, so would I be right in assuming that a regular 1" threaded headset will fit this model and does anyone know if Taiwanese made GTs of that era used an ISO or JIS headset?