We can use my 1LE wheels/tires for example.
I am running 2.4* of front camber (no camber plate) and have about 7mm of clearance from the tire to the strut. Justice Pete has always stated a #2 pencil as a good gauge for clearance. Knowing this we don't want to get any closer to the strut with the max camber. So we have to push all extra width out to the fender.
I use this page for wheel comparisons:
http://rimsntires.com/specspro.jsp
It takes into account the role of the tire in any clearance issues. Some calculators do not do this. And remember some tires actually are wider for any given size, so that variable comes into play. But do not discount the wheel's role, as on the Gen 6's, the wheel may be the first object to cause an issue. So while this calculator is great, it is not a be all end all on dead nuts fitment.
A 19x11 with an offset of ET13 will get real close to matching the 1LE front tire to strut clearance, but sticks out about 20mm. 20mm will poke just a tiny bit with -2.4* camber. I've seen bits of info on custom 19x11's coming in at about 17 to 20 mm offsets. That's not to say they are not using other offsets, that is just what I have found listed here on the forums and elsewhere. Most if not all vendors who sell Forgelines will not divulge the offset info, and I understand that. They did the homework on proper offsets.
If we use a camber plate, we can get most of our camber via the plate and we rely less on the OE point of adjustment at the spindle/strut. This helps the tire to strut clearance because it forces us to pull the spindle (and tire)away from the strut. So we could get a wheel with an offset like 20mm, which on paper puts the tire 7mm closer to the strut, and only 13mm at the fender (less poke). This only works if the use of a camber plates creates atleast 7mm more clearance.
I've added longer studs in case I need to use small spacers for fine tuning. An offset of 20mm may work for me since I could use a 7mm spacer effectively making the wheel a 13mm offset. But If I reinstall my camber plates I could fine tune using thinner spacers if needed, causing the tire to sit into the wheelhouse better with less poke.
Take the above info and apply it to the rear. An offset on the rear of about 40mm on the 19x11 wheel/305 tire also pulls the wheel out by about 13mm at the fender (similar to the front offset of 20mm). Inner clearance is not as big a problem in the rear, but with the ET40 offset we are safe since we know the ZL1 uses a 305 tire on a 11" wide wheel with a 43 mm offset. Very similar.
If we had to use a 7mm spacer up front for good strut clearance, we would also use a 7mm spacer at the rear making the effective rear offset of 33mm, this would push the rear tire towards the fender lip. Compared to the OE 1LE rear wheel/tire combo, the poke is 20mm.
Realistically we want to match the front's track/tread width, which is the outside of the left tire measuring over to the outside of the right tire. This is not a huge deal but the front to rear balance could slightly change. I do not have any experience on how much difference of the front and rear matters.