Technical 56 Pontiac power steering conversion

I have a 56 Pontiac that I would like to convert to power steering. I have read that if you use the 605 steering box, two holes line up and the third have to be drilled and supports welded in place. On e-bay there is a guy selling a power steering box for a 56 Pontiac that is a bolt in. My question is does anyone know what modern steering box (605,500 etc.)And from what vehicle that would be a direct bolt in? Is he selling an oem rebuilt?
http://www.ebay.com/itm/56-57-58-Po...cement-Gear-/121866671724?hash=item1c5fd1d66c

Thanks
Poncho

 

http://www.pontiacsafari.com/L1Garage/SteeringUpgradeGM605.pdf

 

Mgtstumpy

I have seen that article. The guy in the above link claims that his 605 box in a bolt in. I was wondering what box would be a direct bolt in.

Poncho

 

has anyone bought one of these steering boxes off e-bay?

 

If that 56 Pontiac is anything like the mid 50s Olds I played with a 56 to 64 full size Pontiac p/s box should bolt on the frame and hook up to the existing linkage,I know with the Olds 56 was the first year for the smaller p/s box and rag joint.