When I replace axles, I measure HUB face too Hub Face. I tell the seller what axle weight size and also buy new U-Bolts to match as well. And where possible, I "up size +1 as well. re: If warped or broken axle is 3500 lbs axle, I ask for 3800 lbs axle and I "up size" +1 its new leaf spring packs as well. When I get the axle and springs, I then measure my leaf spring saddles location myself and get my local welder guy to weld them on. When replacing axles, don't over think it. Just +1 up size and mount the leaf spring saddles yourself. It's that easy...