Here are some typical applications for 26 and 10 spline discs.
26spline, 10.4" diameter(use as replacement for Mopar 10.5 disc: 82-3 5.0 camaro.
26 spline 11" diameter:'70-4 454 4-spd Chevelle, '78-80 Corvette.
10-spline 10.4" diameter: '70-1 350 corvette
10-spline 11" diameter:'67-9 427 corvette.
These are just a few of the many application for these disc diameter/spline combinations. These are from the Centerforce catalog. Ram clutch has a better breakdown in their catalog but I couldn't find it. I don't know how correct these applications are so you might want to be sure that if you order by application that you get what you think you are going to get.
Also for any of you considering using an O.E. bellhousing with an adaptor plate you might be able to get away with it even with the shorten than mopar input on the Tremec but getting Liberty gear in michigan or possibly Jamie Passon to put a long Chrysler pilot end on the Tremec. You probably need to check how much the input splines move out of the disc(with adaptor plate in place) before going this route though.