26, Front spring clip, is the bolt and/or nut supposed to be square or hex. Suppliers sell hex! (Out of availability?). Does anyone really know?
The bolt should have a square head, 3/8" across the flats with rounded corners. The nut is a thin hex nut, 1/2" across the flats & 3/16" thick.
The end of the bolt should be riveted over after assembly.
Earlier cars used rivets and hex head bolts.
I've been lucky over the years to be able to find NOS or good used parts. These bolts are the same for the front and rear, only the rears are LONGER. As I mentioned in an earlier post, the nuts for these are used in a number of places on late T's, and possibly earlier ones too. The information that David posted above is 100% correct, and I'm happy someone out there is interested enough to find out about this. Also, I'm not sure when Ford adopted this type of bolt, but I would think probably in the twenties.
We sell the correct bolts and nuts for the front.