Is a T-stat housing for a 70 w-30 unique or are all housings for the 455 the same? I know there are cast and aluminum versions of each.

 

They are all the same. There were two versions, the die cast version with the short bypass barb that used the "J" shaped hose and the cast iron version with the steel "J" tube that used a short straight hose to the water pump.






This was a factory change in the late 1970 timeframe - die cast up to that point and cast iron after. Once the die cast housings were purged from the parts network, there was a service replacement kit with the cast iron housing for retrofit on earlier motors with a corroded or leaking housing. Here is a detailed thread about the topic.

This factory engineering order provides more detail for the change in the 1971 model year. Note that the factory authorized the use of die cast housings on 1971 non-A/C 350 motors to use them up. Note also that this is yet another example of how Olds ALWAYS documented production line changes and non-standard configurations. People who say "anything was possible" to justify a one-of-none car are blowing smoke.

 

Thanks Joe, good stuff.