Your post makes no sense whatsoever. I'm not presenting anything. Of course I know that heavy duty Sierra and Silverado exist, why wouldn't I?
You said: "the debate was about what is the top selling vehicle model. The top selling model is the f-series." to which I said, no, the debate is about Ford saying "F series" is the best selling.
The point is: if Ford can include their F150 + F250 + F350 etc which are completely different models and trucks and come up with a stat like "best selling truck", then GM can absolutely include all their 1500s + 2500s + 3500s etc and at that point GM outsells Ford. Do you think the difference between a Sierra 1500 and Silverado 1500 is somehow greater than the difference between an F150 and an F250?
That little sticker which says "silverado" and not "sierra" is just too much and now suddenly they're different models/trucks but the F150 is the same truck as an F250 because it says "ford" on the front?
Think. If you can group all the half tons and super dutys you can certainly group all GM's together too.
As for the Fiat comment, it's not helping your case in the slightest.