Sorry to hear, Ben. The thief had to be familiar with the type of gauges you had, has talked to you about your truck in the past, and/or had you show them how you installed the gauges. So its probably someone you know locally. They've been to your home before.
Did you ever make a thread on your install with pics, like you do for most of your mods? They could have seen that.
When my truck got broke into in the driveway, they were 15 feet from my son's room, and I surmise that the only reason they hightailed it is because he turned his lights on at 6am to get ready for school.