I heard the interior cabin filter was introduced in 2000. Does anyone know if this is true, or were there filters in the ac/heat system in prior years? I have a 94 GC and have a musty/mildewy smell every time the a/c is fired up. Any ideas? Thanks.

There is a spray foam that you can use to clean the A/C. You put your fan on high setting and spray the foam in through the air inlet (on the cowl/by the windsheild wipers). I had to do the procedure on my Neon a few years ago. I think I got the cleaner at W@lm@rt but I can't remember for sure.
The cabin filter was introduced in 2000 in the Chrysler T/C only. Starting in '01 it was available as an option in the other minivans.