I have two sets of Weber Power Plates for Holley 2300, 4150, 4160, and 4500 series carburetors. The carb these plates were on is used on a Chevy 350 with about 450hp. I really know very little about carburetors so I am not sure what jetting the plates have in them and I don't want to mess with them. I just had the carb rebuilt and had the power plates removed and put on an original metering block. I am actually trying to de-power this engine to make it more streetable. I understand that a place called TMP bought out Holley on the Weber power plates and they are the best soarce for gaskets. These are selling new for $300 a set. The primary side takes a set and if you also want to do the secondary side that takes a set also. I have read that you should not do just the secondary side. I have both sets. The PK301 is for the primary and the PK302 is for the secondary. One of the big advantages of having these plates is that you do not have to remove the float bowls to change jets. I also have the original installation /instruction booklet and the longer bolts you need for the plates. I am asking $50 for each . If shipping is involved you pay shipping. You can call me at 408-643-9100. Updated 7/17/13. Thanks.