You're not ANYWHERE near over stocked. At their full size, mollies are only like 3 inches tops, and gourami don't get that big either, 5 inches max. Add some bottom dwellers, maybe a whiptail catfish, some clown pleco, and maybe a you could also look into a fresh water flounder, they only get about 4 inches and they constantly suck on the glass to eat the algae. Keep your options open since you'll have so much room in that 75 gallon. I hope your fish don't get lost in that tank, haha. Good luck with stocking! Oh and also, the angel fish will eat any of the babies the mollies have. If you're planning on making them breed, I'd suggest not keeping angels with them.