Would changing the fan oil in a new fan clutch be over kill?
I'm pretty sure that what you get with the new clutches varies so it's a gamble to just install a new one.
In '07 I purchased a new blue hub and my engine ran hotter with it than the old Eaton I had pulled off. With the new fan clutch the AC was shutting off after slow hill climbs which means temps were hitting the 220 or 225 cutoff (I forget exactly where it is). Once I set the temp and changed the oil in the new blue hub it's worked great. Given how easy it is to check / adjust and drain / fill a fan clutch I would never install a clutch (new or old) on my 80 without setting it up first.
You can get the basics here but keep in mind that mud consensus on this topic has evolved over the years. Most folks run 10k to 30k oil I think and the average oils used have gone up over the years:
History: On my first drive this summer after replacing my transmission I was having an overheat condition with the truck. On the following weekend while towing a camper it was real severe in the 230* range. After returning I was able to confirm that my Blue hubbed fan clutch was to blame...
Here's what I've been running for the last 5 years with success in the SouthEastern US, including towing a 3k+ pound all over, etc. I think that setting the opening temp is particularly important:
small hole 50% open at 110 degrees
45 ml 15k CST oil