I don't think you have to worry about thread size with Momo knobs, they don't screw on like the stock knob. I have a Momo Phantom, and the bottom ring screws off and underneath are three allen screws that you tighten to attach the shift knob. There are different rubber sleeves included that fit inside the knob to accommodate different cars.
If you want something that screws on, look for knobs that fit the Miata, they have the same thread size. I like the Voodoo knobs.
http://www.teamvoodoo.com/Voodoo/Knobs.html
<hr width=60% noshade size=1 align=left><img src="http://gaming.ugo.com/games/images/000000200/37_mainss3.jpg" border=0>
