Is there a difference in length between a power steering and non-Power steering column right now I have a power steering box in my 72 Duster and want to change to manual so do I have to change a column??

yes you'd need the longer MS column cuz the manual box is shorter. People may have broken the inside "tabs" & extended the length of the inner shaft to go from PS to MS but wait for others to advise here. plus the spline nub dia on the box and coupler is different (PS smaller dia iirc & strickly this last (quoted) part is my early A body experience) which may or may not apply to later A bodies but I believe it does & if so you'd need the MS coupler on the end

You can change to the manual steer column if you want but you dont need to.

There are adapters to attach the power steering column to a manual box.

Firm Feel sells an adapter to adapt the manual box to the power pot coupler. The old Mopar one you have to have a manual pot coupler too.

Thanks !