Furnaces?

If it's a gas furnace, there may be brass fittings. Not sure what the burners would be. I took an electric furnace apart and burners were magnetic, though it looked like dull aluminum.

Definitely pull the motor. It adds up quick.

Most furnaces will only have tin value aside from the wire and blower motor. Some furnaces have stainless steel heat exchangers or tubes. Every once in awhile you get lucky and get one with the coil on top.