I have a 67 rag top that was originally a 326 car with manual steering. When I upgraded it to power steering the only thing I replced were the rag joint, the steering box and pump/brackets(naturally), and the pitman arm. Was a simple change that can easily be done in a day if you have everything. I did not need to change any other suspension parts.

As for the speedo I have a 68 in my 67. They are interchangable. So, if you are going to modify your 67 anyway it's not a big deal to swap your 120 speedo for a 160. What you might want to do is save all of your original parts just incase you ever want to put it back to it's original configuration.

I personally love the 67's for all of their differences especially the vent window. Although I did add corner lights from a 69, front and rear, to mine as a safety measure.