Adjusting brakes on my ’29 and needed a way to incrementally depress the pedal to get even braking side to side then front to back. The Jorgensen medium duty beam clamp has a reversible end that allows both separating and compressing. The 24 inch model (about $25) worked very well with driver’s cushion stored in the back seat. Expanding the clamp one step at a time allows fine incremental adjustments. Available at most “Big Box” building material stores or from the manufacturer.
Being a Cheap Charlie, I use a piece of broomstick plus a foot-long section of 1 x 4 lumber with a hole drilled close (about 2″) to one end, hole drilled 1/8″ larger than the diameter of the broomstick. The long end of the 1 x 4 rests vertically against the vertical part of the front seat cushion. Friction from wedging the broomstick holds it in place at any length you wish.