I love elementary OS, and use it my self (and have) for a long time now. However, I would not recommend it for this endeavor. I'd go with something that is highly customizable (and meant to be customized) like Kubuntu, Xubuntu, etc.
Either way, there's a package called MacBuntu
Which will give you a Mac OS X theme and icon theme.
And something called ...
Out of the top of my head, I can recommend this short YouTube video. It contains a lot of information on apps and themes you'd need to install and configure in order to get a mac-like look and feel (window controls position and colors, dock animations, icon colors...).
To that, I would also add the mac-like gestures for the touchpad by using the ...
To install on a 64-bit Mac that uses a 32-bit EFI you'll have to go Matt Gadient's website and download a slightly modified version of elementary OS 5.1. Burn a DVD if you can, the author strongly suggests it. Give the page a thorough read first.
Direct download link for the modified iso md5: 3ded91fadf4a4a450539d1f9332e72a3