Use a mechanical.
I just installed a vdo boost gauge from poston. It is machnicl and was simple to install. It took me about 15 miniuts. You can alson order this exact gauge from kirbans site. for the same price of $48.88 believe. It includes everything you need to hook it up specifically to a grand national/turbo regal. I highly reccomend going with this for ease of installation and accuracy.