I would use a background image of a vehicle manufacturers spec sheet [like that attached], and trace over it using sketch tools......how do you want to use/show this? [are you just exploring it in the 3D model, of displaying it for dimensioned draft sheets, or even setting up renders?]
I have ST8, so can't provide an example file that you can open natively with ST6, but basically the steps are...
Open new part file [if wanting to use sketches only in ASM, then use create-in-place to start....]
Create sketch on suitable plane, place image, position and scale as required, trace over image capturing relevant geometry [I normally place image on it's own sketch, then new sketch for tracing....so I can show/hide the image during tracing]
Extrude desired regions of traced sketch if solid model is needed, or just leave as sketch[s].