Hi Scott, According to Paul Skilleter in the Appendix to hiS XJS book:
March 1988 for 1988 1/2 MY – VIN 147269 Teves ABS introduced.
Also stated as VIN point V12 Convertible introduced.

Therefore I imagine no XJS-C’s were built with ABS, though from Bleasie’s Records there were 80 V12 Cabriolets built in 1988 – I assume these were pre March 1988 build though but I’m sure John B will know more..

regards, Robin