I had a 76 dart back in the early 80's it got flooded to the dash. I cleaned up and drained all fluids but in a short time the engine sesized up. I put a rebuilt engine in and it last a few more years until I got rear ended on a highway.
a buddy of mine from high school used to only buy salvage title cars. he particularly prefered flood cars. i guess because of it not needing sheet metal work. he had a late 90's dodge avenger. it had been flooded up to the windows. he changed the fluids (all of them) and cleaned the interior. never gave him a problem. however, if the car is flooded in salt water.....forget it...its good for parts.