When I did the engine change on my coupe, I re-sealed the oil pan and main seals. You need to get the special anerobic sealant and primer for the pan to block seal (available at NAPA= EXPENSIVE!). I also replaced the entire rear rope seal without removing the crank:
http://www.peachparts.com/shopforum/showthread.php?t=298852&highlight=rope+seal Of course you will need to remove the transmission to replace the complete rear seal. You should use a good degreaser to clean the engine bay before installing the engine. This is the best that I have found available at Sam's Club:
Before cleaning:
After cleaning:
If you have access to a car hauler, I suggest taking the car to your local self serve car wash to pressure wash the engine bay. I took the entire donor engine to the car wash and cleaned it good enough to do a thorough paint job on the engine.