What are safe hi sustained temps

I down sized my turbo from a silver bullet 64 to a 63 71 14 and am seeing way higher egt's when towing. What would be safe or at least doable for a 5 mile 7% grade? I'm seeing 1400 when I used to see 1200 when I dropped out of overdrive. Seems even with the banks intercooler temps are up. It does spool faster but I lost a lot up top when pushing high RPM's. I know 1200 all day is safe but what about 1400>? Slowing down is not an option temps will see 1600 in third!