89 300se transmission interchange

[p7fan]

Hi all!! I've acquired a beautiful 89 300se. The PO overheated it on the interstate. He popped the head gasket AND roasted 4th gear. It has a 722.351 in the car. What can I interchange in its place??? Swapping the extension housing and parking gear (reluctor gear on parking gear for electronic speedo), changing out the "weak link" reverse clutches, and setting the modulator pressures are not a big deal for me.
That's the extent of my auto gear box skills...

Long story short PO had a "flapper" on the serpentine belt that nicked a trans cooler line. It finally sling the belt on the interstate and he drove it until the engine quit and roasted 4th gear in the process. I've repaired the engine and it runs great!! Trans is another story...
Thanks!!
John