water on passenger side only,1997 pu,not drripping from inside

I see in your question that you feel its not the heater core but that is the only thing i have heard of leaking onto the inside floor on the passengers side.

Plain water ,not oily or sweet smelling like anti freeze,cleared ac drain with wire and also blowedout tube with air comp.,,rad.fluid same level ? Have carpet up now and covered floor with baby powder to find out trail of water?will let you know results

did you ever find out where it came in? have the same problem with 1995 nissan pickup, regular cab.