Pete’s assessment is correct. The front seal is commonly replaced without addressing any other transmission internals or the front bushing. As confirmation of the bushing condition, you can examine the converter snout and unless you see some galling in the area where the bushing resides, then just go forward and change only the seal. It goes without saying but needs to be said anyhow, care must be taken when installing the converter into the front pump assembly to prevent a premature seal failure.