I had thought about doing that. seeing as i dont have a garage, nor the tools to do it with i gave up.... This is what i was planning on doing though.
1) get 1 or 1 1/2 inch pipes mandrel bent (keeps then nasty inner bend that decreases diameter) to where they fit perfectly.
2) do a "Y" into a 2 inch pipe that dumped into a drag muffler. The trick here is to put the "Y" in a distance to where the exhaust from each cyl. hits at exactly 180 degs... this way as the exhaust from cyl 1 passes this point, it creates a scavanging effect on cyl 2. and vise versa. Not only will it boost horse power, but sounds great. I will make for a lower note cause the exhaust will be going at a slower speed from the 2 inch pipe...
3) i had planned to use header wrap (keeps the exhaust hot, more volume= more scavanging). I was then gonna make some chromed heat shields, but then that was down graded to no heat shields and use flat black header paint.
there is a formula that you can find on google that will tell you the optimum header and exhaust pipe lengths, but i couldnt get the cam timing to plug into it. Wish ya best of luck and hope to see pics....