20x9 35mm Front, 245/30ZR20 Tire.
20x10 45mm Rear, 305/25ZR20 Tire.

Factory height, no rubbing on all suspension settings.

Front would look better at 30mm offset, its tucked in some as you can see, may try a 5mm or 8mm hubcentric spacer to get flush. They only offer 25mm or 35mm however, 25mm may fit and bring it pretty flush if someone wants to try it. I would also recommend a 265 up front on this, the 245 is kinda stretched but it was my only choice in all season Nitto Neogen.

Does anyone know if I can retain factory length lug bolts with a 5 or 8mm spacer? Or will I need longer lug bolts?

I will NOT recommend 5 or 8mm spacers. They tend not to be hubcentric despite all the descriptions that say otherwise. You run a high risk of vibrations at certain speeds. I am running a 10mm H&R hubcentric spacer and it has no issues (has the hub lip and all). I also ran a 15mm H&R that also had no issues that is sitting in my garage right now.

I will recommend longer bolts (I am running 40mm lugs with the 10 and ran 45mm lugs with the 15). They are cheap and easy to find, do it right

Im adding a 10mm hubcentric spacer to the fronts along with 40mm bolts. This will make the front wheels effectively 25mm offset. As stated above I am running 245 tires up front. I am gonna venture to say the widest you could run up front at 25mm offset would be 255. I dont think a 265 would clear the wheel well liners with the 25mm offset.

Ill post pictures when the spacers/bolts arrive, hopefully this weekend.

Edit: Nevermind, got real confused with dates and timing. Thought you got wheels in a day haha

Glad to see another E running 305s, they look great out back and fit with zero issues (I'm not lowered so I can't speak to that). I'm also running 265s up front on a 30 offset and on tight parking lot turns the outer shoulder will barely touch the fender liner. You won't have a problem with 245s or 255s but a 32 offset would probably be needed with 265s to eliminate the super slight contact but so will a thousand miles of normal tire wear.

Proper offset for flush fitment on W212 E63, IF you are lowered and want no rubbing is:

Front 19x9" wide ET 30 on 255/35/19
Rear 19x10" wide ET 48 on 285/30/19

"Proper" may not apply to different sizes...

Looks lowered. Nice fitment.