There are no 26 spline clutches for that era. So where you are seeing this is not a good source.

It's a 10.5" 23 spline setup and just about any stock replacement kit will do what you need. If you want a lighter pedal feel the diaphragm option is available.

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.