Here are the gaskets that I used: http://www.summitracing.com...sum-620125/overview/
As you can see, they're 2.5" ID header collector gaskets. The Trueleo guys use header collector flanges for the header to Y-pipe connections. That said, your headers appear to be a little different from mine. The size and shape of the Y-pipe is different. You may want to measure the ID of the flanges to be sure.
In any case, several brands and types of header collector gaskets can be found at Summit Racing. And once again, the solid copper or aluminum gaskets are your best bet.