What number in rim size and specs determines how far the rim sticks out from the truck?? May be a dumb question, but I don't know!

 

It's a combination of rim width and backspacing/offset.
Go here.

http://www.bigcustomwheels.com/rt_sp...amp;text2=goal

You can plug in numbers and see how different sizes in tire and measurements in wheel will affect your setup. Make sure your backspace isn't too deep or the wheel will hit your steering knuckle. The larger the diameter of your wheel the lessthis willbe a problem.

sorry for the super long link