Hi Captain25,
I hope Barracuda*s tipp got you going.
If not: I am running sh3 on my old (2010) Macbook Pro. Loading WAC Supermod is a pain in the ass (takes sometimes half an hour) but Lsh3 (15) and Gwx are loading a mission or career mission in a couple of minutes.
I use bootcamp. That is a little more effort, but I guess it is worth it.
Therefor you have to divide your hard disc in two parts. One to use it with Mac OS and the other with windows. They use different languages so they are completly seperated. I first installed on the windows part windows 7 and afterwards SH3 with tons of mods...
Works fine! If you want to give it a try you will find hundreds of step by step helps in the internet. Search for bootcamp...
Greetings
Josef Murnau