Weld collector rings to a set of those 'Race Magnum' bullet mufflers sold by Dynomax. The rings come with about any 'cheap' set of header reducers. (around $14/pair)
The 3" (or whatever size your collectors are) Bullet mufflers cost around $39/each. Get the longer ones for more noise suppression.
It will be a 'little' quieter, and the extra collector length might provide a little extra low-end (launch) power.
A buddy of mine with a Plymouth Valiant went quicker with this setup over open headers. It launched harder.
If you really want to get 'technical', purchase a set of those 'venturi' reducer cones from Flowmaster and turn them around backwards and run mufflers that are larger than your collectors. This 'expansion chamber' can sometimes pick up even more power. Some of the engine builders were doing it on that $100,000 'Engine Masters Challege' anyway... and it seemed to work.
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
[This message has been edited by n2oMike (edited 05-07-2003).]