Started the process on a Rugged Obsidian 45 today. One of my host pistols would be a S&W 1911 with external extractor. Does the internal vs external extractor make a difference when purchasing a threaded barrel? Midway has some Swensons for $70. Also, how do I know which barrel link to go with? I've read that Wilson Combat has a link kit to find the right one, is this the best approach?