I try to keep my EGT below 1300. In the mountains I watch the EGT and slow down or downshift as required. I tow 10.4K 5er at about 62 mph. When the grades are steep 6% or greater I can not maintain 62 mph. I lock out OD and keep the EGT at about 1200 and find that my speed may drop to 45 mph. Check out turbodieselregister.com for more on this topic.
2000 Quad Cab 2500 Auto w/4:10 rear end. DTT 89% VB, TC, Mag HI-TECK Pan, Smart Box, EZ, PAC Brake, Pillar gage mount with EGT, Boost, and Tranny output temp, Miller Manufacturing Truck Bed Cover, with RBW 5er hitch, and
Rigged to tow a 29' Automate 5th wheel.