It was quite awhile ago but I believe I made a slit in the pipes on the headers, swedged in the inner sleeves on the sidepipes and used 4" wide stainless clamps sold by Summit, Jegs, JC Whitney, etc. You will have to break the tack welds holding the 4 pipes together in order to get the clamps on.
You can see in the photo below the shiney inner sleeves and the slits in the pipes.
Here you can see the final install with the clamps.
Don't know if they changed it but you will find that the sidepipe end on the drivers side will have to come in about an inch to parallel the body.
Let me know if you have any other questions,
Roscoe