email this guy, and see if he is interested in a swap..
I'll agree with scartail, don't hack a vintage part without trying to swap it for a the correct part first.
And to offset murphy's law, make the claim that you have just hacked the pipes to make them fit your bike.....so that the member with the correct pipes that would offer them to you only after the fact, will present himself. Then make your swap. I've seen this one in action, and it does actually work.