what’s on top of the front diff cover maybe the oil pan , I could be wrong ?
Ford intentionally set the engine a little bit closer to the P-side frame rail, to maintain clearance from the
fixed position of these 4WD differentials, which sit closer to the D-side frame rail. The older
"Twin I beam" design also had the
floating diff offset towards the left to clear the oil pan above, (so it couldn't crush it when you bottom out). When they updated the 4WD diff design to the more popular current design (where your diff is solid mounted and doesn't cycle up and down), they kept the layout, which also allows you to remove the oil pan easier.