I have a measurement of 6 3/4" from outside the tubes up on the top of the frame. the brackets look to be about 5 3/4" long welded to the top tubes (not taking my seat off) The seat they used was what some of the Taco bikes also used, although the Aggie version bike usually had some glitter style material.
On the foot pedal/scrub brake here are some measurements. Note: I measured outside dimensions
5/8" solid rod/tubing.
9.5" across the from left to right/across the framerail (outside of rod on left to flat end on right.
9" long from foot pedal to back of bend
3.75" foot pedal length
The scrub pad is a 3.5"x3.5" square, welded fairly flush with the rod
Thos bikes used a 4.10x 3.50 -6 " tire (12.5" od) factory so if you play with different tire sizes you may want to set the scrub brake up with tires on and installed to set the angles and spacing where you like it.
That long pice of strap that stick off the right "hinge" stop the pad/rod from rotating too far up.
the rod is retained by some cotter or pins (whatever you like) on either side of the right hinge. ( I think it was pins originally)
Hope that makes sense and will give you some help with it.