Hi getting ready to buy Doug headers p/n D353 i was reading that these work well, my real concern about the steering box, will they clear the steering box and any thing else you can think of thanks Rich here a link to see them http://www.summitracing.com/parts/DOU-D353/
As I said in another thread, the Doug's 353 seem to be virtually the same as the Earle Williams header. I've never had a Doug's 353, but the EW header clears a 605 or CPP500 box - barely (I do have those headers). I did have to grind about 1/16" off the CPP500 box I have in a strategic location. Since every car/every side mount installation is different, your mileage may vary.
Probably the best plan is the new Earle Williams side mount kit that allows you to move the engine to the passenger side slightly. That takes care of some of the diffferences from car to car.
I've got Dougs 353's on my 55 with a Borgeson box. I had to do a little grinding on the box to get clearance. I also will have an issue with the pitman arm hitting the headers. Hopefully I can grind off a little bit on the pitman so my steering isn't affected.