G'day,
as your car has already been converted, the factory holes will now be missing.
I am not sure if RRS can provide brackets to suit converted cars or not, but it won't hurt to ask (i somehow doubt it, as most converters use different drilling templates.
As for which power steer box, use an XF power unit (rebuilt of course) For the pump you have a few options. Personally i like the EA-EL pumps, as with little modification you can use the 6 cylinder bracket as well....windsor of cleveland.
Cheers
Jas