Your easiest route is to use a kit. I used the REZ Engineering kit from Classic Parts for about 60 dollars. It's mainly marketed to the 60-66 guys since their frames are flat also.
It comes with the frame plates you need to bolt the power box onto the flat frame without any dimpling and it comes with the instructions to hook up the column too.
I powder coated mine but here are pictures of the whole deal.
The kit...
http://www.classicparts.com/1960-66-...ctinfo/76-979/