I've gotten some requests for an explanation.
This "valve position vs. cam lobe" is unrelated to siamese or individual ports, cross-flow or reverse-flow, and even occurs in V8 engines.
Cams are made with the unfinished lobes close to their final shape and "clocking" (rotation) and cannot be re-ground, adjusted, advanced, etc.: you're stuck with it.
The cure is a billet ($$) cam (unless there have been many with the same request, such as the Chevy 4-7 firing order swap).
The stovebolt, Gen-3 250 etc., G.M.C. all use this common pattern:
ex in in ex ex in in ex ex in in ex
