Well 'best' may be argueable by many, I can only say what I'm using and like. I switched a while back and after experiencing poor machining quality with two MSD pro-billet distributors I ended up with a Mallory Unilite. I followed their instalation tips (new ballast resistor and a power filter) and have had excellent results. Here is alink to century performances website with listings for GMs. <a href="http://www.centuryperformance.com/mallory/dizzymatrix2.asp" target="_blank">Mallory distributors</a>. I'm sure there are many options out there but I for one am quite satisfied with Mallory.