Hooker and Clifford Hedders

The Hooker Comp headers I had used a thin flange as you describe. They give you a bag of half circle washers that you have to fish between the standard exhaust mount washers and the flange. The top is not real hard, some of the bottom one are really tough. I have seen some people weld the half circle washers to the header flange. It's kind of a half arsed solution. The clifford uses a flange that is the same as the intake thickness, much easier to install. Doesn't matter if it's an aftermarket or stock intake flange, those are all the same. Can't help on the power steering pump, never ran that combo.