Why is this so difficult for you? Ford combines F150 + F250 to create "f series is best selling". Therefore, we can do the same with GM. Add up all the chevy 1500's + 2500's, and all the gcm 1500's + 2500's. When you do that you realize that f series is not best selling.
You refuse to combine chevy and gmc because in your mind they are somehow not the same truck. And my response has been: if ford can combine obviously different trucks (f150 + f250) to create an "f series group", then the gmc 1500 and chevy 1500 can definitely be combined as well because the difference between and f150 and f250 is far far greater than the difference between a chevy 1500 and a gmc 1500.
You bring in all kinds of nonsense about registration, but again if Ford can do it, so can GM.