On the original cars they must mount at certain fixed points so the angle should be the same. What that angle is would depend if the suspension of the cer was completely level.
The only genuine CSX3... that I've seen had an 8 degree layback. The car was on dead level ground, but I have no idea if the suspension height/rake was altered at all.....
(I think 10 degrees looks best )
And anyway, why are you asking this in the Cobras For Sale section ?!?