Slip and slide transmission

Wow! Those clutches have seen some excessive heat. A typical result of a maladjusted throttle pressure (Kickdown) linkage/cable. As CFHJ stated, put in 5 thin frictions in the rev/high clutch drum along with Kolene steels. If you are going to run at high RPM, a reverse wound front clutch return spring as Nick suggested is advisable, or you can go with the bells & whistles multi spring unit fron A&A . Part # K12985BA.
BTW. if you have a reprogramming kit in that transmission I would highly recommend getting rid of the puny low/rev servo piston spring retainer & replace it with a billet aluminium piece. Otherwise you might just surpisingly one day have no reverse gear!
One other thing. Make sure you order thrust washers for aluminium planetaries. if you order the ones for steel planetaries, they won't fit.