A/C- non A/C conversion??

I'm in the process of taking all the AC components out of my 68 Dart. If I get a non-A/C box, will it bolt up to the firewall. I realize the firewalls are a bit different. I mainly just want to get rid of the vents.

Is there are easy way of making this conversion??? Or should I just cap the A/C lines on the firewall, remove the vents inside, and block off the opening where the core is and call it good?