I noticed that the manual for my 99F350 4x4 shows either a Dana 50 front / Ford 10.5 inch rear combination or a Dana 60 front / Dana 80 rear combination is available on the F350. The Dana 60/80 combination is the same axle set shown for the F450. Is this correct? My F350 is 9900lbs GVW but it sure has a smaller set of axles, brakes and wheels than any F450 or F550 I've seen. Has anyone seen an F350 sold with the larger axle set that comes in the F450?