look under the topic coulmn to "attachments" click on that, then go to "Harv's Farm Supply". They make head changers that will allow you to do what you want with your gleaner head.
My experience tells me that the TR-89 would handle a 20-24' header fine.The new platforms with the retracting fingersthe full length of the auger are really superior to the older ones.I think you'll be amazed at the capacity andpower and engine efficiency of your combine.