I fabbed my own rear shock mounts when I put the 9" under my truck. Here's my scientific method for their placement. I held up the original F1 lower shock mounts, measured the position of the schock mount stud and placed my new mounts in the same place. No big deal. I can use the original shocks for the F-1.

If you get a 9" rearend from a 1966-1972 truck it will have the lower shock mounts already welded in place. The trucks before that had the saddle.

It just occured to me as I wrote the previous sentance. Perhaps the lower bracket from any truck prior to 1966 with the larger rear diff would work. Basically you need to find a lower "U" bolt bracket that fits a 3" diameter axle tube.

Bobby