Does such a tranny exist? Check out these links:

http://www.gmpartsdirect.com/perform...ATID=1286.html

http://www.crateenginedepot.com/stor...59-P721C0.aspx

http://www.tlc4x4.com/2000/Conversio...ansmission.htm

And in the 2008 GM Performance Parts Catalog it's listed as part number 19156259

Is it just a typo?

 

Yes 4L80E is a typo. All those listings are for a 4L60E

As for the gear ratio, it's possible to get different ratios in automatics.

 

Yes, I'm an idiot. I meant to type 4L60-E. :-)

Still, I'm not quite so sure a 4L60-E with a 1.75 2nd gear from the factory really exist. And yes, I'm aware it's possible to get different ratios for automatics, but it's been a very rare commodity for this tranny and you would likely have to go to the aftermarket for such a gearset.