I forgot about the posi being available also. The stock 3.90 rear ends hold up well but are not great highway gears. The only other ratio available is a 3.38:1 available from a variety of sources. Some skills are required to set up the gears correctly.
The SM420 is considered bullet proof but all parts eventually wear out. There are parts available as it was a common trans for many years.
Disc brake kits and PS kits are available from various sources also. About $750 for the brake kit including the booster & MC.
About $800 to $900 for the PS when you add in the pump, pulleys, & brackets. labor would be extra of course.
Fred
