Circa 2009 I did this with a G5 Tower (Purchased on eBay for about $60) which was the same design except for some internal differences in mounting. The trick is

Circa 2009 I did this with a G5 Tower (Purchased on eBay for about $60) which was the same design except for some internal differences in mounting. The trick is you buy a PC motherboard mounter intended to be used to make custom cases and you install it in the G5 case. Bam you have a Mac Pro case that will use off the shelf PC components. I ran it as a Hackintosh for a few years but currently it has Windows 8.1 on it. Processor speed requirements have not moved much in that with two GTX 670s in SLI six years later it can still run pretty much every game out there at max settings.