Which road saddles are known for having longer rails? preferably something from Selle Italia. I have a Turbomatic 3 and i'm in the market for a new lighter saddle. One with more setback if possible.

The Arione has super-long rails, but unfortunately it's not from Selle Italia.

Yes, that name keeps popping up. I may have to give that one a try anyway.

But it is from Selle Royal (fizik)...only one word difference...

The Arione has the longest rails.

The original Flite Ti has about +/-1.5cm less "setback" potential than the SLR Ti. That's with the back of the saddle set the same for both, which for me yields the same seated position relative to the BB. In other words, mounted on the same frame, the SLR has about 1.5cm rearward adjustment left whereas the Flite is set right where the rails begin angling up to the nose.

Keep in mind that when you jam it all the way back, you'll more flex. Which you might prefer. But if not, look for a seatpost with more setback and place the saddle on the center of the rails.

As others have pointed out, it is not really the saddle but the seatpost itself that provides setback.
Some of the Easton posts have the longest setback head.

Regarding the saddle: again: Arione, Arione, Arione.
No saddle has longer rails that the Arione, and it is also very, very comfortable to many people.

I'm looking at this picture and it's clear the Fizik is the longer saddle. It seems to me that you can't really sit on that very rear part of the Fizik saddle without your thighs hitting the wide part part of the saddle. I wish I could see how long the actual rails are.

I realize setback mostly comes from the seatpost but i'm going to have to maximize both to get where I need to be.

The Arione extends about a 1-2cm further back for a given seated position compared to most other saddle I've tried including the Toupe, Aliante, SLR, and Flite. And to be more precise, what's being discussed here is not setback, but overall rearward adjustment for a given saddle rail configuration.

The Arione has 85mm of clampable rail.
Most saddles have 65mm-75mm.

Exactly. My new frame has a top tube that is 2cm shorter than my previous one; however the actual distance from from seat tube to the center of the handlebars is mysteriously 3cm even though the angles are near identical. I can go to a 13cm stem and a 25mm setback seatpost but that still leaves me 1cm short. Hence the need for longer saddle rails.

I'd be suprised if most sleek modern saddle designs don't give you that extra 1cm of rearward adjustment over your present saddle.