On Canon USA's website in the 5Ds and 5Ds R details.
Most likely why there are no pre-orders yet.
Makes you wonder if they have shipped or even started manufacturing for the US market.
Bureaucrats always slow the process.

The EOS 5DS R camera has not been authorized as required by the rules of the Federal Communications Commission. This device is not, and may not be offered for sale or lease, or sold or leased, until authorization is obtained.