If you look at the pictures above, it's in the same style 48-55 1st gen truck as the one beside of it.
I don't worry about Summer/Winter weights for Babe, as she doesn't get driven on a full daily driver basis. But I do run full syn oil, which has protections against viscosity loss and thermal destruction in hot running.
I’ve been driving the 58 all these past weekends. The weather is great for wing windows, front floor vents and the heater stuck in the on position… I was ready to change it anyway and have to run a non syn oil with zinc because we used original type seals.
Found this finally. It's not where I got the picture but I went onto Google and searched for '58 Chevy 2dr wagons and then went through a bunch of really nice wagons and found this. Sorry it took me so long https://www.mecum.com/lots/366340/1958-chevrolet-yeoman-wagon/
348CI TRANSMISSION 4-Speed Manual EXTERIOR COLOR Black INTERIOR COLOR Silver MAKE Chevrolet MODEL Yeoman BODY STYLE Wagon From the 2019 Mecum Auction site