Problem with the 60% build is you can't ever sell, trade , or will the gun to someone.
When you die your wife can keep it but it has to be destroyed after that. Seems like a lot of extra work for the small amount of money you will save. Also, the only way to save any money is if you or a friend already has the tools to complete the frame. A good quality end mill will cost more than the $25 transfer fee that a FFL will charge.
1911 frames are not that expensive.
I built a Fusion 10mm and am real happy with it.
I was never particularly interested in building a 1911 from parts, but this site was eye-opening nonetheless... I gather that it will take an immense amount of time and some interesting tools that few have access to in order to build a 1911 from parts.
EDIT - I see that you have access to a machine shop. Good. You'll still need some small files, be able to press bushings, spring, and pins into place, and a lot of time to fit the many parts together.