Colin,
Small Block in a '49I moved the steering box out 1-1/4". I opened up the hole in the firewall enough to let the column move towards the drivers side.
I also heated and moved the bottom of the pitman arm back towards the frame about an inch to keep the tire from hitting the drag link. Don't heat it any more than necessary and don't let it cool quickly.
There seems to be a lot of concern that the steering wheel will be 'crooked' after you move the box out but I was driving the truck daily before the swap and drove it daily afterward and I couldn't tell any difference.
I can get you better pictures of the steering box mount and the hole in the firewall if you'd like them.