Not sure where to get LM online, NAPA had about the best price on it. If you are looking to clean up the engine do it before adding LM, that's just my opinion.
I read in another thread you were concerned with varnish, here is what I'd do. Use a pint of MMO for the last 1000 miles of your OCI. For the winter time run 20% MMO not to exceed a qt for a full OCI. Then add the LM after that.
I'm currently using it in two cars and I'm quite pleased.