What is the dif between AC Core support and Non Air

Well I got this good deal on a core support had it blasted and powdwer coated then read a post about a difference. So how can I tell or a picture would be great.

Thanks

fj

If you look on the drivers side of the support you will be able to see a section that is prepunched so it can be cut out. Look at how the passenger side is and then compare it to the driver side and you will see what I mean. The BB and 73/74 A/C supports already have the piece in question removed. The opening is wider for the A/C and BB cars.