Did you know you can bring in an AutoCAD block into a sketch and keep it a block? Did you know if you had an AutoCAD nested block that it can be placed into Inventor as a nested block? Why would you do this you ask?
Let's take a look at the work flow and I think the last question will answer itself. First let's take a look at a concept layout from AutoCAD that is a block. I have three blocks (base, hinge & arm) that make up a block called assy.
Ideally I want to bring this into an Inventor part sketch and eventually turn it into a working assy. First select the AutoCAD block and RMB to select copy, then head over to Inventor to paste it. Start by RMB and select "Paste" and immediately RMB again to select "Paste Options".
Check the "AutoCAD Blocks to Inventor Blocks" so this it will keep them as a block in the Inventor sketch.
If you look in the Inventor browser you will see that it has brought over the same blocks nested together just as they were in AutoCAD.
From here you can add 2D constrains and see how this will move as an assembly before extruding anything. When it comes time to turn it into an assembly you just need to select "Make Components" from the sketch tab in the ribbon.