The tower is the same as the os and muffler mounting is identical. If you go to the Macs headers website, the have a chart that shows which part number fits which engine. This is how I found out the tower and FX were the same. I know you asked paul this question, but I'll put in ny .02. Get the Webra .50, it was recomended to me by Paul and some others. It has tremendous power, feather weight and is reliable as all getup. Since it has been broken in, I have hardly had to use my starter.

William