Advice on moving gas tank filler neck to new tank

[Toro]

I know the existing filler neck on my original gas tank needs to be re-used on the new tank. For those that have done this, where exactly was the original neck attached to the new tank, on the flange at the tank, or onto the short neck on the new tank? I haven't seen one of the new tanks in person, so I'm not sure how the short necks on the new tanks are attached. I hope my description makes sense, thanks!

[A1971Blazer]

remove the two nuts on the flange...
then you can heat the flange area to melt the solder and it will come right off...
obviously make sure there's no fuel or fumes in it....
or just take the old one and new one to a radiator shop they can do it.

the flange and neck is one piece