I purchased Armours Siamesed pipes for my 63 Super Rocket.
I can't say that they fit well, the bends are anything but smooth and the left pipe enters into the head at an angle of about 15 degrees, nothing can be done about it. This puts the finned heat diffuser at an angle to the head rather than in line as it should be. Bugs me every time I look at it. Maybe one day I'll tackle building a set from stainless, then I'll only have myself to blame if they don't fit!
Glen