That's not an easy request. You can watch Auction Arms and GunBroker and when you find something that you like, call it to our attention and we can give you our two cents worth of advice. It is pretty much a buyer beware situation out their, so it is up to the individual collector to learn as much as possible about the "subjects of our affection" before we start shelling out the big bucks to buy anything. Also try to befriend some serious, veteran collectors that won't mind showing you the ropes, so to speak. If you handle many correct, original pistols, you will soon be able to spot something that is not right and maybe even fake, very easily.
If you don't have a copy of Charles W. Clawson's Collector's Guide to Colt .45 Service Pistols, that would be a good starting place. Go to http://www.coolgunsite.com and order a copy. That and a very informative CD that has literally 100's of untouched pictures of 1911s and 1911A1s, will cost you about $60.00.
Oh, I forgot to ask you.....what's a 1911A1-A4?