when I retrofitted the gauges on mine I cut off the back of the stock metal enclosure and welded the aftermarket gauge bracket (to the back of the pod) cutting it to fit the outline of the pod. That allowed leaving enough of the stock pod enclosure so that the gauges could sit behind the stock plastic lens cover.
I thought about doing something similar but, not really going for the full finished look on this rig. Just going for the quick and dirty so I can get her on the road. She'll end up being a streetable toy. My 72 will get a lot more attention to detail as it's going to be my family oriented daily driver. Any chance you could post up some pics? I'd really like to see how that turned out. What size gauges did you end up using?