A 255/85R16 is about a 33x10" tire. The stock tires are probably the 265/70/R16's, which is like 31x10.5". The difference between a 31 and a 33 is about 6.45%. 4.10 gears are 5.13% lower than 3.90, and 4.30's are about 10.3% lower, so the 4.10's would be the closest match.

However I doubt you'll notice all that much difference, especially w/ the V8. You will slightly lose some acceleration, and your speedo and odo will be a tad off... but as you say, the V8 should be able to handle it just fine. Think of it like you're driving around with an extra 250lbs in the bed (approx. 6% of 4000lbs) or an extra passenger or two.

I ran 33x12.5's w/ stock gears and a V6 and it wasn't that bad. I didn't think it justified the cost of regearing anyway. With 35x12.5's and stock gears, its another story though (but still perfectly drivable).