Nosferatu

As title states...I found a smoking good deal on a set of tires but want to know if they'll fit...

I have stock C6 narrow body rims at these dimensions/offset (with stock tire dimensions)
18X8.5/+56 w/245/40/18 (25.7 diameter) tires
19X10 /+79 w/285/35/19 (26.9 diameter) tires

I'm looking to throw this size tire on the rim...do-able? I need to know so I can buy them.

305/30/19 (26.3" rolling diameter from 26.9)
265/35/18 (25.3" rolling diameter from 25.7)

Will these fit and will the rolling diameter be okay for active handling system?

RC4G

Doing down in height < .5 inch in height shouldn't cause an issue but I would be more concerned about the difference in widths.

not08crmanymore

If you have an auto car the speedo might be off with wrong size tires. Manual tranny,it corrects itself...

Nosferatu

I'm a manual and could care less about the speedo. I'm getting a retune on the car soon and I'll correct.

I'm concerned about tire width fitting a narrow body with rubbing and concerned about it overall fitting on the tire. Will I need spacers?

Thoughts there?