Steering Conversion Early A body

Another related question on the gear boxes. If I did stay with a power box:

I was told that basically all gear boxs manual and power are the same and will mount. I know you need an adapter for manual. However I know that some later models had the larger sector and I want to know if I get a power box from a 70 E body that has the firmer feel faster ratio will it work on a 64 Dart? Running a 71 Dart from disc system complete with TTI headers on a 416. I think the only issue I am aware of is the pitman arm. I know that the fast ratio arm will most likely hit the headers, but is there an arm that supports this size box on my setup?

I know it is suppose to also be an even swap on a 73-76 A body, but I do not know what other issues for the 64 running 71 parts.

thanks!