Ok smh my bad luck. I need to swap out my crossmember with Brad92SE crossmember cuz his is modified for the dp and manifold. But 1 of my bolts jyst spin cuz the weld on the nut snap off.

I was thinking about cutting a hole small enough to reach the nut and hold it down so i can take the screw out.

 

Is this on the radiator end of the firewall end?

If the radiator end, easy, just cut out an "access panel" to access the nut and weld the panel back on when you're done. Obviously you should tack weld the nut back in place too.

Maximan190 had pictures of this exact type of "access panel" in his restoration thread if you'll do some searching

 

Radiator end

 

these bolts right?

mine were rusted out and not many good threads left on the nut so i had to cut open an access hole to weld new nuts in -

 

Those are the exact pictures I was talking about/remembered from your resto thread