Larry,
I have two of them. The one that I loaned to Tyler is made from a piece of DOM tubing with a flange that bolts to the pinion support area of a 9" chunk. The other is a store bought one from Mark Williams and it is made from 4130 tubing with a semi machined cast aluminum pinion support. I also have an 8 3/4 Mopar chunk that has a flange added to the pinion area to match the end of the bars.
Roo