Which throw out bearing??

Put a SM465 GM behind a 231 v-6 and used the stock GM bearing but the clutch does not disengage at all. Put a bolt in the clutch fork to pull it to the bell housing but no luck!! I probably have half to three quarter of an inch run room on the front out put shaft before the throw out bearing touches the fingers on the pressure plate. Is that too much? Is there different bearing thicknesses?

 

There are many different ones. Read this The Novak Guide to Clutches, Linkages & Bellhousings for Jeep® Conversions scroll down and there is a chart and numbers that might help. If that doesn't work buy their adjustable one Novak Fully Adjustable Throwout Bearings as Patrick stated.