Is the firewall on an ac car the same as a nonac car? Can you change to a non ac heater box with out modifications? 1967 Camaro.

The firewalls are different for ac vs non a/c cars and modification would be necessary.

Thanks for info.

I'm currently looking into the same thing.
Detroit Speed and Engineering (http://detroitspeed.com) makes a cover plate for a 'smooth' conversion OR the easier route is to saw off the a/c box and leave a 3" stub, keeping all internal organs in tact while glassing over the top of the box.