Hello. I really need some help. I have a 1970'd model Rheem gas furnace. I need to replace it, and have a possible furnace, but am not sure. None of the dealers can find my model number. It's RGMA-100C. My house was built in the 50s, on a slab. The heating/cooling vents are on the floor. I have central air also. I am very low on funds, and a friend gave me a furnace they couldn't use. I may have a guy to put it in, but i need to see if it works first. Here's my question. How do I know if my current furnace is a downdraft or updraft model? Can anyone find this model number? My friend says the new furnace isn't set up to use with central air, and that it's an updraft furnace. I need to know if my current furnace is in fact an updraft furnace, can I still use this furnace she is giving me if it doesn't support central air? I mean, I know obviously my air won't work, but can it still be hooked up. Please help, my furnace is busted, I live in Ohio, and it's starting to get cooollldd.