1992 gleaner r72 header

Hello I am new to the gleaner combines but thought I would take the green blinders off and give one a try. Anyhow I recently bought a 1992 r72 and today I picked up a gleaner 7000 straight cut header. When I tried to install it on the combine the feeder house is the right width but the feeder house is about 4" shorter than the opening on the header. Is there an adapter that I need to get for it to fit or is there something else that I need to change. The salesman I bought it from said it would fit, I hope he was telling the truth. Any information would be greatly appreciated. Thanks

1992 gleaner r72 header