My older mobile home doesn't have the 4" base extension (Part # 100738) being so old and the newer furnace has one on it. Do I need it or just put the newer furnace right on my exsisting floor,any information would be helpful. Maybe I could call you to find out more.Thanks inadvance.

We do not have any call people here. If it fits on the old base, you can usually retro fit without problem, however, the new heater may require the 4" clearance for UL, CSA or ASTM approval. Read the install instruction closely.