GM used 2 different bolt lengths that I have seen and the length was dictated by the ICM (the L36/L67 I've always seen same length and pitch, but GM may have had mid-generation changes I have not seen) and the 3100/3400 had another length (but same pitch.

Sir, we're going to have to agree to disagree. The L36/3100/3400 through all generations/years used the same exact coils. The L67 from my knowledge for all years (I believe spanning '96-04) had a completely different coil. You can validate it by a unique part number and underneath these are the onl coils with blue plugs to connect to the ICM.
When people do top-swaps, they typically don't change to the L67 coils because the gains are minimal.
But these coils are different. I have 3 sets of coils in my garage (from L36 and two 3400's all the same part numbers) and L67 coils on my Monte, Grand Am and wife's Impala that do not match the original coils.

As I said, if you still don't agree, that's fine, again, I think we can safely agree to disagree.