I used a 2.5" overlapping band clamp on the driver side pipe. There's a walker part number and you can order them through o'Really's. The part number is 33226.
Dynomax Performance 33226 - Walker Lap-Joint Band Clamps - Overview - SummitRacing.com
I'll find a picture of the other clamp if I can. The biggest thing is you have to find a clamp that is shorter than a band clamp (width), but will still fit in between the Y on the downpipe.
Also, the 3-bolt flange gasket is the same as most SBC header collector gaskets. You can pick them up at any parts store in the performance section. Get some good stainless bolts and RTV, along with at least one band clamp and some other clamp for the other side, and you'll love life. Mine are so quiet...I can't believe I didn't fix them earlier.
I might see if i can snap some pictures of them for ya