Which is the best Bevertail safety to put on a springfeild 1911 milspec.
~Thanks

I suppose it depends on if you want to alter the frame or get a drop in safety.

Best in terms of what?  There are quite a few of very high quality.  They each have a different feel to them.  I like the Ed Brown part because off how low it sits the gun in your hand.   You may think it sucks.

Most of them are too high and I can often grab the 1911 and have it not go off.  I like the not-so-high one, Kings, a good photo of it on this page:

linky  Definately a Kings in the photo.  I have fitted several of them.  They work with my huge meat hooks.

This is a minor consideration, but Springfields, the Miml-Spec included, have grip tangs that have a lower than normal top surface.  What that means is that most beavertails will have a higher top surface than the frame after installation.  It's strictly cosmetic, but unless you go with one of two aftermarket beavertails, the top of the grip safety and the top of the frame cannot be blended to match, unless you weld up the top of the tangs.

Those two beavertails are the Smith and Alexander .220" radius, and the Wilson Combat.  Of the two, the S&A is much easier to fit, due to the .220" radius, as opposed to Wilson's compound radius.  

Outside of that, I'm a big fan of the Ed Brown.  The same smith in wildearp's link installs them with barely enough to black the trigger bow, which he refers to as his "sensitized" installation.  It works great.  

I used an STI beavertail, and the Brown fitting jig.
Caspian frame, so it's the .250" radius.

Wilson Drop-In
Works well, and no frame modification is necessary, but they look like crap IMO.

This one requires filing the frame, but if you take your time they come out very nice:
Wilson .220" Radius

And if you go with the .220" radius, you'll need this:
Wilson Beavertail Jig
And a good set of files.