The Hedmans I am using were orignally installed when the car was manual steering. A year latter I swapped to power steering. There was no clearance issues with the power steering but it is much tighter.
IMHO, the best way to install the drivers side header with power steering is to remove the steering column (it only takes 15 minutes). Then unbolt the steering box from the k-member. This will allow you to move the steering box over and out of the way. Place the header in place and bungy it tight to the block, this will give you room to bolt the steering box back inplace. Then bolt the header up and reinstall the steering column.