N14 or C15 or ??? for good power and MPG?

Hey guys i want your opinions on this....I love the fuel economy my 97 detroit 12.7 has...always high7 to 8+mpg at 70-75mph with any load under 30k and puts out decent power at 475 pedal & 500 cruise , but lets be honest the overhead cam design isnt ment for low rpm pulling up long mountain grades and even dies down alot sometimes in high rpms up steep 7-8+ percent grades .... Eventually i was thinking of engine swapping my Century so i can put out some good power and have strong jakes to head out west into the big mountains later on cause the loads out to oregon/washington always pay really good and those loads are easier to book since a fewer percentage of truckers go out west.....only reason i dont get them now is because i dont have jakes on my engine and thats scary in the mountains with any load or even empty. I could put jakes on my engine and possibly up the power a bit but i know detroits are very limited to power unless you fully build the engine like pittsburg power did with that kw they have on youtube making 650hp but that will possibly be costly and can maybe spend a bit more on a nice rebuild cat engine that can make that power stock internals.

 

Your brave man, ive done lots of steep grades in co, wy, az , nm , pa , oh and wv but lots of braking and 75+ moments.... for some reason my truck loves to accelerate hard down steep grades....be nice not to cook my brakes often lol

 

Hey man thanks for vote of confidence....yea i mean this engine has been really good since i got it rebuild over 2yrs ago, however i did hear some tapping noise on cold start this mourning but ive heard that before and its the oil....i dont get it though i just changed the oil last 2 weeks....i already put about 5k miles on it....think this mobil oil is basically water lol

Yes i need jake brakes, currenty saving up for that....idk about going out to oregon/washington with any load without jakes....i know its possible but want to save my brakes longer.

I had a 6inch stack a bit ago and i noticed a better pull after 1400 but i saw lower mpgs so i took it off...maybe ill put it back on eventually.

Also i got 2.9 rear gears with a 13speed which i know doesnt help in the mountains and thats another 10k to spend on a swap

 

Yea i already have a 75mm borgwarner, need a tune and jakes.

 

Yea think i just need some higher rear end gears cause 2.9 is really low for mountain grades and well ive 300hp max so far on the scan gauge with this ecu....my previous ecu i saw 475 around 1600-1700rpms climbing. Also before had a 10spd with no overdrive .... Now got a 13spd....