The gauge buckets on the 54-55.1 models are secured to the dash using three studs that are welded to the back side of the dash. Remove the nuts holding the assemblies in place and they should come out.
If your pop is replacing the gauges with 5" quads he can use the old gauge buckets to mount the new instruments. I have some pics of how I did this on my picturetrail album. Here is the link:
http://www.picturetrail.com/sfx/album/view/19808900
At this time I would not recommend using the Dolphin gauges I used as the lighting levels between the two instruments is way off. They say they are fixing it but I have not been informed the fix is final as yet. Other than that the dolphins are acceptable instruments for the price.