The task is not as difficult as you might think. A couple of good books exist to help you through the process. One is "Hallock's .45 Auto Handbook," and the other is Kuhnhausen's "The Colt .45 Automatic - A Shop Manual." Try the Brownells catalog for the books, and also for a number of parts and jigs and tools. "Shooting Times" also ran a series on building .45 a few years ago.
The first thing you need to decide is whether you are building a basic shooter, or a match fitted .45. With an aluminum frame, match fitting is not a consideration unless you opt for an embedded rail system (not something self installed).
One of the beauties of building a .45 is you can start with a basic version, then add bells and whistles as you save up the $. When selecting parts, also consider whether you are building a "Series 80" style with firing pin lock plunger system. The Caspian frames I've built on do not have the provision for the plunger business, so I make sure the slide does not either.
Triggers jobs can be done but only with the help of a sear jig. A good one for the $ is the Wilson jig, available from Brownells and also from Gil Hebard Guns, 125-129 Public Square, Knoxville, Illinois 61448. Fitting a thumb safety can be a bit tricky, but a grip safety is a little easier. Beaver tail safeties are not too difficult if you have a jig for the correct radius, and the guts to start grinding on your frame.
For the .45's I've built in the past I've generally done most everything except refinishing the pistol, and silver brazing the front sight. I've farmed out barrel fitting for the ones that had an integral feed ramp on the barrel and the frames had to be machined for it. Kart has a kit for fitting their barrels that Gil Hebard sells. Reviews of the easy fit kit rate it pretty high.
Good luck with your project. Having made it with your own hands will provide you a pistol with special value.
