A/C vs. Non-A/C firewall and cowl differences?

Hey guys, I'm looking to ditch the A/C box in my '68 bird for a non-a/c one. I have a great non a/c core and controls but I'm noticing a lot of differences in the firewall. Like, none of the holes will line up for mounting or heater core. No big deal, I can take care of that, But I'd like to know if the hole in the cowl where the heater box takes in "fresh" air is in the same location so I can at least position the non a/c box correctly to mark all of my new holes for mounting and heater core lines. I just want to take the extra weight out of the car, don't need a/c and I don't think my motor will pull enough vacuum to operate the a/c box correctly. Thanks in advance!

I'd say the fresh air location would be the same but I don't have one to compare to be sure. By the way your car is the first 68 road runner with air I've ever heard of. Cool.