Hey all,
    I just bought a pair of SA 1911's, one a Mil-spec 5", the other a 4" Champion, both parkerized.  Since I a) have big hands, and b) am a lefty, I need to have beavertail grip-safeties and extended ambidexterous thumb safeties on both guns.  Can I get some recomendations on which products would fit the bill best?  I'd like to stay with black parts since both guns are parkerized.  Also, do the grips have to be modified for the extended ambi thumb safety?  If so, I will want to replace the grips with the ones I want on the gun prior to having the safety work done, is that right?  Thanks!

Also, a good recommendation on where to get these parts would be greatly appreciated.

If you go the beavertail route, you need to decide whether you want a fitted beavertail that requires cutting the frame, or a drop in.  Fitted is nicer, but there are some pretty nice drop ins out there.  Fitted will also mean you have bare metal when the frame is cut, so you will also need to decide if cold blue is acceptable, or if you want a total frame or gun refinish.

If you go fitted, there are two that will fit the non standard rear frame tangs of a Springfield.  They are Smith and Alexander (the .220" radius) and Wilson Combat.  Others will work, but will sit higher than the top of the frame, which is unsightly.

Of the drop ins, Wilson Combats drop in is the most popular.  Kings makes several different styles too.

Most ambi safeties require that the right side grip be relieved underneath for proper function.  It's very easy to do to your factory grips, or you can buy ones that are ambi cut.  There are three ambis out there that do not require grip mods, and those are the new Kimber pinned ambi (as seen on the Warrior), the King's, and Mueschke.  Nobody uses Mueschke anymore, though they were once popular on Colt Custom Shop guns.

Personally, I would go with S&A beavertails, Ed Brown ambis, and cold blue on the frame cuts.  I would wait to refinish the guns after I was sure no more custom work was being done.  However, this route will be pricey if you're not a do it yourselfer.

The best single source for parts is Brownells.  The Kings and Kimber parts need to be purchased from the respective companies.  Midway is also a great source for parts.