Leaking fresh air box??

Just noticed today that my fresh air box door when I opened it in the driveway was full of water?? The carpet on the floor was drenched. I think the stupid sponge rubber donut I bought which seals it around the lower cowel pan is leaking. I ran some water in the outside cowl louvers and sure enough water started dripping down into the fresh air box. The seal is brand new. Is there some way to tighten the heater box upward to maybe stop the leak or am I on for the remove the whole heater box deal. Oh, it is a 72 a/c car as well??