The only headers that fit an early A with PS without any mods are the long discontinued Clifford long tubes. The front 3 tubes actually route before the PS box through and under the K Frame. I have a NOS set of them that somebody tried to fit them in other applications and finally gave up on them and stuck them on eBay since he had no idea of what they fit (I knew so immediately bought them). I believe Aussiespeed has basically re-invented them with some minor improvements but rest assured, they are not cheap - something like $5 or $600 plus shipping from OZ.
Your other alternative is to find a set of Clifford shorties and modify the front tubes to clear the PS box OR replace the PS with manual steering and then they drop right in.