There is no quality plastic panels for B bodies. Except bucket seat back panels sold by some restoring shops like Classic Industries but these are available just because are shared with 70/72 E bodies. These are in fact molded in color, not painted. GRRRRRREAT pieces. Dunno the manufacturer.

The other manufacturer aside Palco/Dashtops is Accu-Form.. (Accu-$hit is how I call them) which are even worst

Tony’s sells now A pillar panels which seems to be good pieces, but never have seen them in person.