I did a mechanical one in my 03. Pretty simple. Just dropped the pan, drilled a hole in the side and welded a nut there for the sending unit to thread into. The hardest part was running the line without kinking it, and making sure that the sending unit wouldn't be touching anything inside the pan.
The pan may not be the best place to mount a gauge to get an accurate reading, but I couldn't find any other place that was doable.