What exactly do you mean by a match lower? You should obviously install a match trigger of which there are many out there. Then, you can use some KNS FCG pins which I would call match quality. There is even a set trigger option FCG. There are match grips available - the type used for match shooting with contoured grip and hand rest. Other than that, there is not much to do to one. The receiver itself can be mated tightly to the upper, though that does not effect accuracy. To do that, if they are loose to begin with, a tensioning pin or accuwedge will tighten it up, or you could start with the RRA Match Receiver Set - they are mated together for tight fit. I used a match upper half in a build of mine, and a regular lower, and the upper was very tight - so tight I had to use a mallet to separate them the first few times but now it pivots easily yet there is no play when they are closed.