Oldsmobile Cutlass Supreme

I have a 1968 cutlass supreme that I am thinking about trading (not sure about selling). It runs great and is a solid car. I drive it just about every day. It has a new radiator, voltage regulator, fresh tune up with spark plugs, wires, cap and rotor, alternator, headers and after marker exhaust, deep pan B&M transmission pan. Still has the original spare tire and jack in the trunk. It has air shocks in the rear from factory. The bad about the car, is the transmission has a slow leak when it sits and the interior needs redone. Engine is a 350, th400 trans, but i also have a 455 big block on an engine stand that will go with the car. I rather trade then sell but for the right price I would sell. I would want something that runs. I would like to find a 67 impala or an early 70s trans am, or charger? Let me know what you have. Im only interested in American muscle from the later 60s early 70s. Asking 5000 obo if I were to sell.