Blacksmoke

What is the weight of the 05-06 18 Roush wheel? It is not listed on their site and phone rep cant help either...
I had to put 18x10 tires (stock were 18x8 or 9 i think) on the Roush because they were a bit bigger and would not quite fit.
What about the 06GT stock wheels?

How much slower will it put me if they are heavier?
Will I still be able to take a stock 05-07 350Z with these wheels?

Thanks