73-87 springs on a 71?

[Jason71k10]

I know this has probably been asked many times before, but i'm pretty sure the search is still down so.....

My passenger side front spring is sagging and I can get a pair of front springs off a 78 3/4 ton for free, so i was wondering if they will fit on my 71 k10?

I could get the pack rearched, but if these will fit and they're free, i'd rather just swap them in.
I measured the springs on the 78 and they were 48" long and 3" wide, but tapered to 2 3/4" in the center. I don't think the springs are that wide on my 71, but it's not at my house, so I can't measure them.

Can anyone tell me if they'll fit??