Mixing exhaust parts
 

The previous owner of my bike put a V&H slip on muffler on the stock exhaust. The headers are looking pretty old and rusted, as well as the mid pipe, so i'm thinking they may need replacement in the near future. Does anybody know if most aftermarket headers and mid pipes are similar enough in their dimentions that i can keep the muffler? For instance, a quick internet search for F2 headers found some D&D exhause systems (header, mid, and muffler). If i bought just the header and mid, would it mate up to the V&H muffler? Or would i have to by the complete system.