I know nothing about these companies but they sell them: http://www.droppedaxles.com/FORD_AXLES.html http://pmtfabrication.com/Products/134-1953-1960-f100-cnc-machined-tubular-dropped-axle.aspx The search function here will probably turn up some other options.
I'm picking up my new 60 this wedensday. hopefully dropping it this weekend. its a must they sit way to high.
None better than Sid...but I'd slide a late Crown Vic aluminum under there...lowers it and bolts in with 6 bolts! Ford must have planned that one...it's on the F100 truck site.