Technical 1958 pontiac auto trans casting numbers

Help, I have a transmission supposedly from a 1958 Pontiac. It is covered with gak. Where can I find casting or id numbers to verify? It is a slushbox.

 

I assume "slushbox" denotes a Hydramatic transmission. There should be a metal tag attached to the side of the unit with two rivets. If for a 58, the stamped number will start with P 58 and then the serial number. PA 58 denotes a fuel injected car.

 

Thanks, which side? Towards top or bottom?

 

I believe mid passenger side by 58.

 

Thank you, sir!

 

Handy tip: If it is not on the passenger side it will be on the drivers side.

 

This is 1957 however I suspect similar to 1958. Actually a stamping, not a casting.

http://pontiac.oldcarmanualproject.com/manuals/1957/1957 Pontiac Hydramatic Service/index.html

 

Awesome! Thanks to all!