Need advice regarding a MCG's detail set

I wonder how I should go ahead with the photoreduced gauges. Do I try to take up holes in the panel and mount from behind or do I just grind away the plastic gauges and put the new one there instead? What I'm talking about is what you can see in the pic below.

Best regards.
Niclas


http://img.photobucket.com/albums/v332/proosen/American%20Muscle/General%20Motors/Chevrolet/1958%20Impala/Instrument.jpg

In most cases it is easer to make holes in the dash and mount the faces behind the dash, then it is to trim the faces to fit the holes.
http://files.automotiveforums.com/gallery/watermark.php?file=/502/73480Porsche24progress.JPG