I have one-they are built by Mallory. I forget the max mechanical timing that may be set but I set mine to 20 degs and run 16-18 degs initial. the springs that come with in are probably a bit soft for a decent engine as the mechanical advance comes in quick...seems like it is not much over 2000 rpm. I dug around in my junk and swapped in a chevy spring to slow it down a little. Timing is a bit twitchy in the middle of the curve as well. Some say this is due to the weights not being heavy enough to give a stable, repeatable curve.
If the the Firecore had been available, I think I would have gone with it if for no other reason than I like the HEI terminals that you can get with it...best idea that ever came out of GM, imo. I believe it comes with some extra springs and it has an adjustable mechanical advance as well. I forget the limits on it but I am sure their site probably shows them. I think it might be a bit better designed unit but I have not seen anyone actually mention one. I have read they use a couple of ball bearings to stabilize the shaft which gives a more precise positioning with regard to air gap which is nice as well.
I think the MP one is no longer being offered but is available from suppliers.
