The "Cup Car" discs are not more expensive than the OEM parts.
Some things I've learned about 951 clutches:
(i) There seems to be only one current factory part for the clutch disc. It is the same for all 951's. It has four large springs, and a secondary damper plate with six small ones.
(ii) Regarding above, the six small springs have a habit of breaking long before the clutch is worn out, eventually causing the clutch to fail to release. I have a "like new" '89 951, and these rascals just broke in December at 26k miles!!!
(iii) I've put "cup car" clutch discs in both my cars. I have the Sachs and Porsche part numbers for those interested. The dealer does not sell these discs.
The key differences from the current factory part are:
(a) only the four big springs are present, i.e., there is no extra damper plate
with springs to break off;
(b) the friction material and method of bonding seem different.
After having two clutches prematurely break their springs, I'll never use the current factory type. The "cup car" type can be had for the same price.
SACHS part number: 1861 944 433, 3000 513 001 (three piece kit)
Porsche Part number: 951 116 011 09
The other factory clutch parts (pp, throwout and pilot bearings) can all be used with this special disc.