If I read your post correctly, the heater core has not been connected for some time. They may have been disconnected because the heater core was leaking (and if you think replacing your kick panels was fun, try the heater core). I recommend you attach a couple of pieces of heater hose. Plug one end and attach an air fitting to the other and apply a small amount of compressed air and listen for a leak under the dash in the heater box. You don't want to attach heater hoses and then find antifreeze leaking onto the passenger side floor board.
