Manual Steering ratio, recommendations? 16 or 24 to 1?

Wanting to switch to manual steering but not sure what ratio steering I should go for.
Car is 75 duster glass hood and bumper, iron head 360, with 165 tires on the front.
I had 69 dart with glass hood, and 185's up front, and 20-1 steering which I felt was pretty heavy parking with a 13" steering wheel.
So I'm not sure if the slightly lighter duster with slightly skinnier tires would let me go to 16-1 ratio, or should I go 24-1, which my only experience with is my D100 which is pretty easy steering with 245's.
What your thoughts and experience?