The length of the 98/17500 nozzle is the same length as the 98/11000 nozzle. I did testing on a 98/17500 nozzle that was about 1-1.5" longer but there was NO real increase in numbers. What I did was order 98/11000 nozzles and core them out for the 98/17500. You can use an AMW nozzle length for the 98/17500 if you want.
Thanks everyone. I ended up machining it to 3.10 inside the case length and then the exit cone, but the problem with that was that it was underexpanded because of the exit step diameter, so I opened it up and got rid of the stepped part so it has a more optimal expansion.