hello.ive got an old 3 ton 3 phase condensor unit that im gonna replace.i also have a slab type evaporator that is very dirty and old.the transition from the furnace to the evaporator is crap.its just a bunch a foil tape and patches.anyway,ive been doing a little research.but i dont know which coil to use.can i buy a coil with a plenum already attached?should i get a slab or the "A" coil type?my system is horizontal in the attic.horrible drain issues.ceiling almost caved in last year.i think i can handle the condensor unit.and whats the difference between a heat pump and a a/c condensor unit?i replaced all the duct last year with bran new stuff so i know for sure everything after the evaporator is totally sealed up.but just wondering which evaporator will cool the best?