Remflex crush gasket is the ticket. I also have the Motiv overpipe and the front pipe and the Remflex gaskets have been leak free for the last 50K miles. I also use them between heads and header, header and overpipe and midpipe to axleback.
This is the one I used for the overpipe to front pipe:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
You just have to enlarge the bolt holes on the gasket a tiny bit, since the bolt pitch is slightly smaller on our cars.