when i did large centrals in my 220g i had a few vieja,(blackbelt,bifat,melanarus,synspilum} a few parachromis red tiger moto, loiselli, freddy) and some amphilophus Red devil, lyonsi. as far as the convicts my experience with them was mixed they are extremely prolific and will try to breed very often and young. i personally kept my other archocentrus in different tanks because of that.
This is the kind of mix I would go for Really nice fish there.
I would stop worrying about mixing these fish in this size tank especially at just juvenile sizes its just not a problem IMO.
Also if your after just a CA tank Oscars are mainly SA and the Bichir is African.