Great stuff guys,
I am considering buying a 58 6 cyl auto truck and swaping out transmissions and all the other associated parts. I think this truck has the posi rear as it doesn't look like the round Eaton style cover in my 59.
I would be more inclined to think the diff wasn't original if it isn't an Eaton, as the Posi option wasn't available until '59. The '59 Posi trucks did use a different rear diff, the Spicer 45 that was also used in GMC 1/2 tons.
