Biggest problem with the brake savers is they put allot of heat into the oil. At least that's what I hear from the old timers I never have even seen one in person
i have drivin a few old trucks with the brakesaver....the old ones leaked like a sive, never really heated up the oil though course they would barely slow ya down empty too fer the kind of runnin yer talking about 2hellandback, i would go a min of 475hp, 13, 15 or 18 is really up to how much you wanna shift....but the 18 would prolly be better for the getty-up-go grunt yer likely to need....taller rears wouldnt hurt to much either for gettin goin grunt sounds like yer thinkin of doin a gig kinda like one i looked into a fer years ago....hualin mine stuff in double pn tanks...looked like a good gig
People dont release and reapply enough,in the old days the radiators were never big enough. My oil never gets above 240*F on a hot day going down a big grade I also have a 1500 sq inch radiator,that helps.
Thats could be why you never see a C15/16 do any more than 500,000 miles before it needs a rebuild over here.
Even the acerts dont run that hot here, mine will run 150*F on a cruise and the MOST it will get to is 200*F on a hot day running the hills, then once i coast down them it cools back off to 150-160*F. Sure them WS gauges are accurate?
Personally, I would run 550 cat or larger, 18 speed, 3.90 or even 4.10 if lots of good grades, I know fuel can be a concern, but when you up horsepower and lower rear end gears such as 3.58's something is going to give later down the road. Sometimes a heavy haul program installed in the ECU will actually give you more balls on the hills and even save you some fuel. If you can't make a good living at it, don't do it.