Rod, I ran an 6RN New Idea head on my R52 for a few years, it worked very well. It is a gearbox head and did a good job. Pretty sure I still have the adapter if you need one.
Why not just go with a 630 Hugger corn headIJ Might cost more but I think it would be worth it when it comes to resale and besides they're very good heads. I didn't know they put Cat engines in R52's. You sure it's not a CumminsIJ
Your correct ...I meant Cummins. The Hugger seems to be about 10K higher. I am so tired of that orange head that I dont want anything to do with that again. I dont care so much about resale as I will keep the combine for 15 years but I want a solid low cutting head.
Comparing your orange head to a hugger head is like going from an outhouse to in-door plumbing. Hugger heads are low profile and very reliable. I would highly recommend the Hugger even though it costs more. That's my opinion. Good luck which ever way you decide.
I have 2 R-50's. I have a black head for one and a hugger for the other one. There is absolutely no comparison. The hugger will walk right through down corn that other heads won't even run in with a reel. If it were up to me there would be no decision to make because the hugger would be the only one I would consider.