Trying to finish up re-flowing the driver's side header (T/A Stg 2 SE). Have 3 out of 4 tubes cut/fit/and a combination of tack-welded & clamped. My Buick has rear-steer; the box behind the crossmember, and this entire re-flow debacle is because of that very fact. A mirror image of the passenger side might have worked just fine. At this point, the 3 tubes I have in place are 'cupping' the PS box, and get within a 1/4-in of it in spots. No question I'm going to have to lay the header in there, then drop the motor in. Likewise; not going to be able to slip the PS box in with the motor/header there. I intend to have the headers ceramic-coated when done, but I'm wondering if I'm going to need some sort of heat sheilding or even add thermal wrap to the pipes in that area, to keep the PS fluid from getting too hot.
Look at any of the rear steer F and X body car headers. They fit pretty tight against the power steering box also, maybe as close as your dimensions. You could always have them ceramic coated. That helps keep heat in the header pipe and can't hurt.
Funny you mention F Body and the rear steer! Just went thru this at work on a ‘68 Camaro, boss kept ordering the cheapest SBC headers off eBay, steering gear box was in the way, after looking at pics, I saw the tubes are bent around the gear box on rear steer cars, still had to remover the box, but they fit like a glove. I had him order the headers from Summit Racing. The eBay ones aside from being wrong, the tubes wouldn’t allow for regular plugs, would have to use shorties, plus one bolt I had to cut to half it’s length to get into the hole, PLUS EVERY hole in the flange had to be wallowed out.
You’re gonna have to ding them up for best fitment then. No loss in power. You definitely want some space there.