Cylinders running too hot

yellow rose said
When they are that far off at an idle it's usually an intake manifold issue. Most times it gets amplified with RPM but I have seen some stuff that had wacky distribution at idle that cleaned up as RPM went up.

If you are going to really sort it out it should go on the dyno.

Also, I could be nuttier than a jar of goobers and it could just be a tuning issue.

I've been wrong before.

I don't think you are nutty. A lot of times with older dual planes you can get all four corners looking just right but the center four cylinders all end up looking bone white. It's a distribution issue that usually pushes you to having the the outer Four Corners a hair fat to get 4,6,3,5 looking decent.

Intake work could be in his future.

But to be blunt I don't not sure why he's worrying about 500 Degrees, I usually tune the idle as to not stink to the best of my ability and so I usually run my idol just 'fat enough', as in 'on the lean side' and end up with temps around 400 and 500. I think it's when it reaches over 600 that you got some tuning that will hurt you over some time. I wouldn't worry about those higher temps he has @ idle as i would wonder about the lower being too fat at idle. Remember it's not under any load.
See what it does under load @ RPM like 4000-6500