I started by checking the clearance between the rudder pedal bracket and firewall recess (photo 1). There is a little clearance, but just to be on the safe side, I added another 3/32". I then drilled the rudder pedal bracket to the vertical firewall stiffener, and drilled the center bearing to the bracket in all three positions. The fit check is good in all three positions (photo 2).
I then started fitting the center floor stiffeners. I finally figured out that the difference between the left and right stiffeners is the amount of offset in each end. The forward end is offset to clear the 1/8" thick horizontal angle at the base of the firewall. The aft end is only offset enough to clear the 0.040" thick flange of the F-704 bulkhead flange. I marked all of the stiffeners with FWD and AFT to help get them oriented correctly.
I had to notch the forward ends of the vertical legs of the center stiffeners to clear the center vertical firewall stiffeners (see the image in the mirror in photo 3). With the forward stiffeners clamped at each end, I back drilled the holes at each end of both stiffeners.
Clearance between the rudder pedal bracket and firewall recess.