To answer your question about the H pipe. No it won't fit. The H pipe listed there is meant to be welded onto your stock cats so you can add on duals. The H pipe sold there is exactly what I bought to have my single exhaust setup converted to duals. The H pipe there is shorter then other H pipes (because it's made to weld on after your factory cats, just cutting out the Y pipe and nothing else)
I would search for a new H pipe setup. Find either a set with or with out cats your preference. Make sure you match up all your pipe sizes correctly and find a set that has the falanges on both ends. That way you can do the install your self.
If needed let me know and i'll try to dig up the pictures I have of my dual setup and you can see what I mean about that H pipe being welded onto the stock cats on my V6. Just PM me or post back here. I'll keep a look out. Good luck with the install...I guarantee you'll love duals.