You will never find a 144" wheelbase T1N Sprinter in CAD.
T1N Sprinters were only available is 118" 140" and 158" wheelbases. (2002-2006 Sprinters were the T1N style)
If you want a CAD Drawing of a 144" wheelbase Sprinter, it will have to be an NCV3 (2007-2014).
CAD really pays off if the data is used to produce (via CNC) actual parts for the build. I have over 100 CNC tool path files for plastic and wood parts that were machined for our interior and other items. Many of the sheet metal parts were laser profiled and then formed with a CNC press brake.
The roof outline of the grabcad models for the 170" early in this thread were wrong. Unless you get one that was done very well or directly from MB, you will only be able to use it for planning, not to CNC cut to fit. Here is a 3D printed section from the CAD file compared to the real roof section. It's way off in places. I tweaked a piece of the model for this section for my purposes, but to fix the whole thing would be very difficult.