Here is a page that link to a thesis that shows that Gallo Italian is not a part of Italo-Dalmatian but a part of Western Romance and connected to Rhaeto-Romance.
http://www.squidoo.com/linguistic-unity#module157223241
It doesn't seems to be actually a convincing thesis (and didn't convinced lot of people, outside a guy in internet that say "i'm fond of Mr. Hull thesis" on his webpage. At this Mr. Hull is unfortunatly the only one to praise both a "padanian" language and saying it's not only connected, but totally the same between raeto-roman and gallo-italic.
Not only the raeto-roman group is clearly acknowledged to be independent from gallo-italic as much any other language, but the whole use of "padanian" language is hilariously wrong, as it its strangely connected to electoral borders choses by the Lega Nord.
Indeed, the venetian dialect is known to be totally distinct from gallo-italian, being the transition between italian and dalmatian.
Furthermore the use of "padanian", apparently it was used because he didn't have another word, and didn't wanted to use gallo-italic (admitting he wanted to show an unity between raeto-roman and gallo-italic group). Let's admit the use of "padanian" is an unfortunate choice, critically concerning the use of this word by the Lega Nord.
That George Hull want to show an unity, it's his right. But for now, his position concerning it is minoritary (i didn't saw any other name attached to this theory). For the majority, there's no nord-italian language (there's northern italian dialects though, separate from Italian) and even less an unity between Gallo-Italic, Venetian and Friulan-Ladino-Romanish.
What strikes me in his thesis, is the extensive use of morphology at the cost of grammatical and lexical base.
In fact, all the first half of his thesis is about morphology. If it's about showing the morphology was similar, everybody knew that.
Again, maybe you have your reasons to think it's a better scale to use mainly morphology for linguistics, but it's not the case for the majoritary. It's not because you're favouring Mr. Hull for some reasons that you can ignore the massive agreement on the absence of unity. Because, no, it's apparently limited to the thesis of George Hull and some italian linguists.
Furthermore if you actually read his thesis, a part showing the phonologic and morphologic similarities of northern Italy only, you'll see he's talking about a reconstructed padanian language. What he's proposing is an unified language, something NOT existing OTL, and he admit it. His main concern is to protect northern italian dialects, and for that he say "here's a proposition to speak padanian, instead of being divided".
Of course, as it's not paying attention to the grammatical and lexical differences, it's flawed from the beggining.
So to resume : nothing is said about unity or disunity of grammar and vocabulary (except by passing, and without a real concern), the "padanian" proposed her is admitted to be a reconstructon based on the dialects but never having an actual existence (a part Lega Nord linguists that extansivly use that for their purpose, everyone in north Italy talk or "Lombard", or "Piemontese", or "Venet", but no one say "i'm talking padanian".
So : you can't have a padanian language as described here as it never existed really, or at best otherly than "potential language".