First, Champion (not to be confused with American Champion) came out with an STC to convert the IO320 engine to make it have oil pressure inverted, this was for the 7KCAB. It was STC7CE, basically a "trap door" in the sump with a pivoting oil pick up. This system was also used on the 8KCAB when it was certified in 1970, it used the same system. Then in 1975 the Decathlon was fitted with the Christen inverted oil system and an AEIO 320 Lycoming engine replacing the IO 320 engine.
To answer your question, no the 7GCBC is not certified for the Christen system, and it would not be of any use as the engine would not run inverted anyway as it doesn't have an inverted fuel system.