If he is your friend, you should ask him directly what parts he is using...... And he shouldn't have any issues with telling you. As far as lower parts kits go, most are made to a mil std and are pretty comparable....made to be cheap, safe and reliable.
Without knowing what your build goal is (other than price and some reasonable expectationof quality) and intended use, who knows what you will get. The platform has endless variables and you should be very specific if trying to build a custom rifle. To me, the joy of building a custom rifle is all about getting the specific things you want.
Good luck and enjoy. Also,don't sell yourself short on being able to do the job yourself... There are countless resources available that can walk you through the process of a simple build.