I can't find the message I sent to the ebay seller. I think we went with 15/32 for the internal bore. I think 7/16 would not fit, but 15/32 has a small bit of slop (it is taken out by the set screws, but it is there).
I'm so sorry I just saw this. I'll get it to you if I can.
hey i just read your $30 custom shift knob. I'm in my shop class and would love to make my own custom knob. Do you still have the measurement for the size of the actual shift stick? with that id be able to make a collar with set screws like you showed here.