evaporator core

I'm in need of an evaporator core for my '92 Corolla DX. I haven't removed the bad one yet, but have been making the calls to find a replacement. The aftermarket guys are telling me that there are two different types; a plate and fin style and a serpentine style. I called Toyota to get the scoop and they said their info doesn't go into that much detail, but that there is only one part number in their system for '90-'92. No one has one in stock to look at, so that's out of the question. If I were to gain access to the one in my vehicle, what am I looking for in telling one from the other? I could buy the one that Toyota sells and be done with it, but I haven't found a money tree as of yet that would justify paying double what I can get one for.