Congrats! You'll love your 75 gallon tank

Get Angelfish instead of the Oscar. You can have a few Angelfish in a 75 gallon tank, but Oscars ... you could have only one in a 75 gallon tank. Besides, with Oscars you need frequent and large water changes ... so unless you're willing to do that in a 75 gallon tank ... better get some Angels instead.
I suppose you could have around 6 Angels in a 75 gallon tank, but I personally will have only 2 Angelfish in my 75 gallon tank. If you get an Angelfish pair, they'll be happy together, just the 2 of them. If you get more Angels, there is always a possibility that you'll get 1 or 2 mated pairs, and the rest of the Angels without a mate will be bothered by the mated pairs. Mated pairs breed regularly, and when they breed, they become more aggressive than usual (trying to protect the breeding site and their babies), especially towards other Angelfish. So, you need to be careful with that.
Of course, remember to CYCLE the tank first! And do not overstock! Good luck
