Not quite sure what you mean by altered??? I only have one pair of 340/360 manifolds left and the 360 in this pic is sold although the 360 exhaust manifolds I sell are all the same casting number as seen in these pics. The 360 manifolds I sell are all identical. I machine them so that the exhaust hole is basically ported and smoothed out to approximately the same size as the 340 driver. I have sold out of 360 manifolds but am in the process of making more. The 340 manifolds are much harder to get but I can get them, prices may vary. I will sell the 360 "machined" manifolds separately for those folks who already have a 340 driver. But I only sell the 340 manifolds paired with a 360 "machined" mag. NO serial numbers are altered. If you use the hot key in my other post you'll get more info.