I am doing the same thing on my 71. I have been buying individual components for mine but Bouchillon has a complete kit. The only reason I did not go with their kit is I wanted a Firm steering box. I would recommend finding a power steering column instead of modifying your original. Put the original aside along with the gear box.
http://www.bouchillonperformance.com/inc/sdetail/7794/7821