Understanding the Leica M8

Good morning. I don't actually have a Leica yet, but I'm considering buying an M8. Since I'm looking for a CCD sensor for everyday use and I find the M9 too expensive for my budget.

But I have a question, which may seem stupid... The lines that we see in the viewfinder, since they are equal to a 28mm, if I put a 28mm on the M8 knowing that there is a crop of 1.33 should I still trust its lines there? Or should I rely on the 35mm line instead? I'm quite lost, could you explain to me?