DO NOT polish the feed ramp of your 1911 if you don't know what you're doing. You'll turn a working gun into a nose-diving POS.
45 Auto is 45 ACP (less common 45 AP). At most stores it's sold next to 45 Colt (45 LC) which is revolver ammo. 45 GAP is for Glocks.
1911s aren't exclusive to 45 ACP. I'm assuming you don't have a 9mm, 38 Super, or other 1911.