I know that the later R107 seats from a 560SL will fit an earlier 380SL or 450SL. I'm not sure of the SLC seats will interchange, although I don't see why they would not.
These may look a little lairy for some tastes but I would consider them for my SLC given that the original seats are not really that comfortable.
And at $479 for a pair in leather, it's not a bad deal at all.