Just as well no OEM cats are available anymore, as those likely would have been the older pellet type of cat. Current aftermarket cats are (nearly?) all the honeycomb type, which used to be sold as a "free flowing" aftermarket upgrade by Magnaflow/etc.

Also, the only difference between "direct-fit" vs. an equivalent "universal" cat of the same size/spec for the same vehicle application is that direct-fit come with mounting flanges already attached, whereas universal need to have flanges welded on at the proper overall length to swap in for the stock cat, or can just be welded into the exhaust piping directly, sans flanges.