I think my C10 rear axle has a 2.5? rear gear ratio / is this true

[G-NUT]

I was given a rear axle from my mother-in-law's boyfriend; it came out of a 1984 Chevrolet C10 2wd that he's had for years, but it's been sitting in his field for quite a few years. I just tried the whole mark the drive shaft yolk and wheel hub and spin / count thing from all the YouTub videos I've found, and what I seem to come up with is 2.5? . I have an open diff. I've never heard of a truck having a gear ratio higher than 2.73s. So is there a 2.5? that would have been in the truck. I asked the guy I got if from if he'd ever changed them out and he said no. There is no tag on the axle to help me identify what they might be.