Hope you get an answer, but I'm not sure any members here can address it directly. The header issues are relatively new since the trucks are only now getting up there in years. I think you have a significant gamble if you want to try the 3.5 header on the 3.7 as there already seem to be some reported fitment issues on aftermarket vs. OEM.
Considering that every reseller I've seen (at least ones with clear cut definitions in their ads) shows different headers for the 3.5 vs. the 3.7, I suspect that the two are not interchangeable. What manufacturer is going to come up with two different products (with identical performance goals) for the same application when only one will do? R&D, tooling, etc. isn't cheap.
But if the savings is worth it to you - potentially putting it in, pulling it out, sending it to a machine shop, putting it in again, etc. then go for it. Someone's gotta be the guinea pig :wink:
2006 manifold part #
12571601, 2007 #
12604221. The 2007 part does not list any backwards compatibility, even though it fits the Canyon engines as well. The 2006 part does not list forward compatibility with later years, including on Canyons.
Maybe it will work, but GM can be strange. For example, I learned that a 2006 4L60E is not fully compatible with a 2007 H3. The changes may not always be obvious, but they can be enough to prevent it from working properly.
