I made some changes implementing Retro Computer Tinkerer "Poor man's S-Video" on the C64 that have only 5 pins video output, since pin 5 (AUDIO-IN) on the video connector is rarely used, I decided to use it for chroma instead, this is the schematic:
I had to remove C12 and solder a wire between R14 on the VIC-II side to the negative pad of C12.