A Mag 24 on a 75g is so far beyond overkill it surprises me that you haven't had a flood yet......or you have a ball valve on the discharge and have it restricted so much so that the flow is reduced to the 600 gph that a standard 1" overflow can handle.
Bottom line, get yourself a Marineland Euro Utility Pump 3000 or a Mag 7 or Mag 9.5 (if you're sold on Mags) and you'll run your pump efficiently without restricting the flow.
when i went to get my tank the lady had a bunch of stuff so i grabed that pump cause the price i could not beat it was 35 dollars the tank was 50 so i said what the heck n i figured that if i went with a bigger setup i would need it
That is a serious pump, I tried it on a dual overflow 120 and it was way too powerful. You can cut the flow like Russ said with a valve but IMO you should try and sell or trade for a mag 9.5 or something equivalent
Im using a mag 24 on my 210 and ill probably throttle it way back plus use it to drive most of my filters and also circulate water in the 120 sump/fuge...if you wanna sell it or trade lemme know I have new mag 7s and a new mag 9.5