68 non a/c to A/C

[mo]

well fellas, recently i converted "caroline" no a/c dash to A/C for a number of reasons. 1: the PO had cut out the radio holes in order to install a new radio.
2: i found a good/cheap a/c dash
3: i want the option of having a/c
4: i had a killer am/fm radio i wanted to install
the question i have now is that i have researched the steps to convert the firewall in order to accept the original type A/C condensor box.
Of all the post only one mentioned that there was no need to cut the fire wall at all!!!
This individual has done a number of them without cutting the firewall at all...
has anyone done it this way...i mean, why cut it for the sake f cutting if it doesn't make much difference and its hidden.
please let me know your thoughts. and btw going with aftermarket is not an option. I want factory original...
thank you