A 90 would not be ideal, but could be done depending on the personalities of the individual fish and how much maintenance you are willing to do. I had an Oscar with a couple large severums and a jack Dempsey (and various temporary fish) for years in a 90 gallon, the tank got dirty a bit quick but I had no aggression issues. If you were willing to do a 50-60% water change once a week, or two 40%, I think you would be okay bioload-wise as long as you didn't overfeed.
The issue would probably be with the JD and GT imo, if they were both passive it could work out well. If one of them becomes an aggressor, you might have to remove a fish.