Welcome to the forums, Juanico!

Pushing the nuts out carefully is the best you can do.
For that you could use the next size bolt.

I don't like blind nuts.
For the firewall, I prefer using regular nuts epoxied to the back of the firewall.
Sometimes, there is no enough room in the tank compartment to do so.

I live about 25 miles from you; just send me an e-mail if you need my help.