Build 6.4 or 5.9/6.7 conversion build
 

My 08 6.4 has 208,000 miles. It's starting to begin to have all the BS coolant pressure issues as usual. I have an h&s mini max, dpf ******* with 5" straight pipe, CAI. EGRs are still present but "turned off" in tuning. Getting to my question, would it be a better insterest in money to completely build my 6.4 (pushrods, pistons, RCD valve springs, h11 studs, bigger injectors, basically everything but connecting rods cause the price is outrageous) or should I do a 5.9/6.7 cummins conversion? I'm looking to get 700-1000 reliable HP out of this build.

Yes Do it, The 6.4 is too problematic and damn $$$$$$ to fix. The fuel system is very touchy. International didnt build those motors to last. I.E no bronze bushings in the rod where it spins around the journals. The regen in 7&8 cylinders is a bad idea and bakes the turbo seals causing them to fail. Do a fummins. go 5.9

i've seen some pretty cool 6.7 conversions in 6.0 a lot easier and cheaper to build a 6.7 and if you get a harness from painless a conversion is pretty simple