Removed Cross-Over Plate 66 Stang

He broke the heads off of all 6 bolts...

Schooner, you need to post these updates and clarifications in your original thread about this issue. When you start a new thread every time nobody knows what you're talking about and what the context is.

As best I can tell, it looks like the broken off bolts are still in the nuts which are part of the floor. If this is the case, you need to carefully drill those broken bolts out. Soak the area in penetrating oil, and start with a 1/8" drill bit as close to centered on the broken bolt as possible. Then start stepping up drill sizes. This often breaks the broken bolt loose so you can twist it out with a pliers. If not, once your drill bit gets close to the actual size of the bolt you'll be able to remove it. Try really hard to minimize damaging the threads in those nuts. After the broken piece is out, run a tap through the threads in the nuts and you should be good to go. Just take your time and it'll turn out OK.

You'd be better off leaving the crossover plate off altogether than fastening it on in such a way that it cannot be later removed.

Also, clean all that gunk off the bottom of the car before welding the new floor pans in or the welds will be no good.