Fitting footboxes?

[Three Peaks]

What is the secret to mounting the footboxes? I seem to have forgotten the secret handshake or magic words or something?

I have Tim Gunning's footboxes and I can't seem to get them to fit up perfectly. Also, once I have them close, I can't seem to get the top lips lined up so the firewall will line up. I've got them almost in place but not sure where to go from there. How do they mount relative to the 3/4" square tube? Does the driver's footbox bolt to the 3/4" square tubing?
I also have the Tim Gunning firewall and I wonder why I can't seem to get it to fit once the footboxes are in place? I thought it wouldn't require trimming since it is predrilled for the mounting holes and punched for the birdcage and wiring entrance holes.

Has anyone else been through this and how did you manage these pieces? No instructions with the parts so I'm counting on you guys to guide me through while I still have some hair left!

One of the reasons I really need to get this right is I am using the Wilwood hanging pedals and need to find a mounting system for the pedals in the footbox somehow. But I can't design something until I get this part figured out first.

Thanks,
Bob