There is one 15 and one 6 pin power connector off the RK11 backplane. The PDP 11/05 NC style chassis does not have these, so you'd be better off with the PDP 11/05 S style (BA11-K) chassis if you want to install RK05 drives on your 11/05 system. The PDP 11/35 or 11/40 chassis has plenty of power ports, the RK05 would not be a problem for these.
I picked up a RK11 backplane in better shape, here is a photo of the two I own here. Not sure why the backplane wirewrap is different.