Depending on the width theres quite a few combo's for a 5ft tank. Oscars will go with clown loach, but as davo points out the growth rate difference may be a problem.
In the end it depends on the width of the tank before any solid stocking option can be suggested, though going on the assumption the tank is 18" or 24" wide other tank mates could be: silver dollars, clown loach, smaller plecs, apolo sharks to cichlid tankmates like severum, earth eaters, sajica, blue acara, green terror, fire mouth, convict, rainbow cichlid, salvini just for examples. Though the personality of individual fish will differ, and some options will be more risky than others (salvini, GT) and should be monitered carefully as the fish mature.