Dan Silbaugh is our diesel guy. He has rebuilt one himself, and he lives at altitude. His seems to run pretty well. But if you really want to go up to the tunnel at 65, you might be shopping for something other than a 40 series. There are a few 45 mph stretches in there for most of us 40 guys.
Sascha Steinway TLCA # 20217
1977 FJ40 "Ripper" (because it shreds!) (What is a "shread"...Steve Crase)
1988 FJ62 "Dino" OME, now in the hands of my daughter
2013 F-150 "Black Ops"