3.5" is the "standard" pre-91 backspacing. 91-97s LC80s have a 0 offset on an 8" wheel which is what a little under 4.5" (115.4mm) backspacing stock, right?
Anyway, stock width is a 275 vs 255 which is 20mm (0.79") thinner, 10mm bump out.
So I would think ~4" backspacing would put the 255/85r16 at about the same outside position as stock. 3.25 would push that tire out quite a ways IMO.