Offset/Backspace on OEM 15x8 Rally Steel rims from my 87 C10?

[cyberpine]

Anybody know what the Offset/Backspace is on my 15x8 OEM Rally Steel Rims might be on 87 2wd C10?

Currently running 31x10.5 tires and they seem to sit way into the well.

I'm looking to run Steel 15x10 Cragars with -44mm Offset and 275/60/15s tires on it.

Also, can anybody comment on how much wider at 275/60 tire will look on 15x10 vs 15x8? It would appear to look signficantly wider from the trucks I've seen on the road.

According to the calculator it's 10.8 wide by 28 high. I use to run 275/60 on 15x7.5, and it looked wide, but nowhere as wide as when I saw it on a 15x10.

Thanks.