Yes, but it may be costly unless you fabricate. Harv's farm supply (bish) had adapters and drives available. The adapter is fairly complex as it changes the pitch to the ground and the feeder hole is offset. The drives are just pto shafts with a female hex on one end to slide over the JD shaft, which you will need to cut back and install their supplied hanger bearing. Change the reel drive hose ends gleaner. They also have a harness and box available to make auto header height function if your combine has it. It used to cost about $500. I have a complete adapter setup but don't want to part with it. I think the website is harvesfarmsupply.com. Or just google it and call for prices. Also you need to add flighting to the auger for the smaller feed hole and remove some fingers. I think that about covers it.
I've only ran rigid headers but I am assuming that the 500 series header is the same as the 400 rigid header when it comes to the drive shafts behind the header. The 4/500 series has only one drive shaft on the left side of the header for the sickle drive. There is no shaft going out the right side to drive the reel as it is hydralically driven from the machine. The 300 series has this shaft to drive the reel from the end of the header. If you bought a 500 series you would need to mount a shaft along the back side along with a resovior and motor since I don't believe your n5 would have the capacity to drive the reel hydralically. Maybe someone on here could back up what I'm sayin since I really have never been around a flex head. We briefly tossed around the idea of putting a 400 series on an N7 but was told by the dealer it wouldn't work unless it was modified like I said.
Hi Matt. You are right but I can borrow the pump kit i have on my rigid head. We are looking for a 20 to 25 ft header. Here in eastern Canada, 300 series headers that large are rare. Our N5 has auto header control, suppose it will work with the 500 series.
Gleanerjunkie brings up a point I missed about the earlier machines needing the header-mounted hydraulic system. Thanks. If it wasn't for that, I was going to suggest that you price everything out before you gave up on the idea, but I think you would be money ahead even if you have to travel to find a gleaner head. Good luck.