Jim,
It is like almost all parts, original Ford parts, if they can be found and/or restored, are better than almost any repro part, including side mount brackets. You know an original side mount bracket will fit the frame holes and have the correct arm shape. Original side mount brackets come up on eBay on a fairly regular basis. Bert's in Denver has a lot of original parts, so you could check with them to see if they have any available.
Rusty Nelson