im a intermediate/advanced mogul skier looking to buy some specialty mogul skis what size should they be im 5'8 145lbs
I would recommend you get something shorter. I'm essentially your size and ski 163cm Volkl Supersport Allstars and 161cm Icelantic Shamans. I plan to buy a new pair of skis, 90mm waist, camber and early rise and they'll be about 170 but they'll ski shorter. You don't need nor necessarily want longish skis for bumps.
We used to ski 203cm Rossignol 4S slalom skis for moguls back in the late 80s although I don't remember how. 174cm Fischer Watea 84s work well for me now. One of my all time favorites was a 172cm Dynastar 8000. Too short is not an advantage if the moguls are big. I have done most of my mogul skiing at Mary Jane in the last 25 years. I'm 5'11" and 165lbs so 165cm to 170cm seems right for you. Keep in mind some specialty mogul skis are designed for competition mogul skiing which is a whole different thing than recreational mogul skiing and might not be right for you if you use a more rounded turn style. Others more up to date on current skis and technique might have better insights.