I have researched in this forum and found that towing up a hill and hitting 1200F on EGT is not a big deal. But hitting 1350 for 30 seconds is a limit one shouldn't exceed.
I sometimes tow up some mighty long hills. Since adding the 3000GSK and my new fuel plate, the engine has the power to tow my trailer up a hill at any speed I care to, within reason. I consider EGT's my limiting factor now. I now know enough to just back off when I hit 1350. But on some long hills I could keep it at 1200, 1250 or 1300 for an extended amount of time. Can I run 1250 or 1300 for 10 minutes without worrying? (I have been afraid to do that to date, I slow to keep it below 1200 down instead. Am I too conservative?)

 

you can 12-1250 all day long if you wanted to. Anything over that you need to limit.

 

I run 12-1300 every day pullin the work trailer. I see 1800* sled pullin too. I did pull 3-5 mile hills last fall quite a bit and seen 1600-1800* from bottum to top. Head was off recently getting fire ringed and the cylinder walls still have the cross hatching.It is a safety thing to keep egts below 1300*, but I guess im a not very smart.

 

I used to have the same problem towing heavy.
Snow's water meth injection fixed it right up, now I can pull any hill at the speed limit.