They also made a 7722 as the larger hillside combine offered. I've seen more of those in the Palouse than 6622s
Here’s a couple ideas, these machines are for sale in my area. The 9610 has a John Rea conversion, which can hang onto hills pretty well compared to some others. My cousin has a Case 2188 with a Rea leveler. Only a few were done to red machines, the rest were Deere.
https://ironsearch.com/equipment/for-sale/1989-john-deere-7722-combine/3645364
https://burlingamemachine.com/product/jd-9650-hillside-w-930r-header-cart/
https://burlingamemachine.com/product/1998-jd-9610-hillside-conversion-w-jd-924-header-cart/