In the 74 Duster with a floor 3spd, do I need to add the floor hump to put a 4spd from a 84 Aspen? I read the article that Doctor Dodge sent,the link, but it wasnt real specific in the 74. I am kinda just trying to see how hard or involved this swap is going to be..

Your factory "3 on the floor" hump should be fine for the 4-speed.
If you current 3-speed bellhousing has the dual bolt pattern then you have it real easy, just remove the 3-speed and plug-in the 4-speed.
You may want to swap your speedo-gear from the 3-speed. Also check the "slip-yoke" size, there are two different sizes that could cross you up.
DD