1968 Chevelle Console Installation

Hello, I am taking the shifter off of the colume and putting the console and shifter on the floor, How can I tell if I have the horseshoe shifter and console in the right spot, Not to far ahead and not to far back, are there any kind of measurements of some sort, Its a 1968 chevelle and its a 1968 console thats going in it. Also there is a harness with a couple of lights in the console and the plug for them only reaches just outside of the console, Is there another harness for it and where does it plug in? Thanks Duckie