woodstock is correct.
LPK's are generally the same from one to another. Even if your LPK is marketed by a well-known AR-15 manufacturer, it's probably made by another company.
The biggest variant I've seen in LPK's is the fire control group, specifically the trigger and hammer. For instance, you can buy a LPK that has a RRA two-stage trigger (at least, you used to be able to...when you could find them), instead of a standard GI fire control group.
BTW, I've also cobbled together LPK's from various sources. It's a PITA, but do-able.
My take on LPK's is this...you should always buy one more than you think you need. Those pesky little detents are easily lost, and springs have a tendency to jump around on you too.
