frame help please

[chad29]

I have made a few post recently about taking my lwb and converting to a swb and have received a lot of responses on it. Thanks for all the help. I have searched all over the internet for some more detailed instructions and pictures but have had no luck. Someone posted a link of how they did theirs and it shows and calls out to make the first cut behind the crossmember at the rear where the cab sits on. Mine does not have a crossmember there. It is a 77 gmc sierra grande. it just has an ear on both sides and not a crossmember. Why would me chasis be different???