Of the original 4 little gauges, I now have a pair of VDO CHTs (can you be too paranoid about CHT with a 140?) and an electrical OP. The OP was the most "difficult." It's mounted in the lower right and required some small modifications to the support behind the dash. All in all it was pretty easy to do. They look and work great. I'd like to get a tach next, but the stock one works and isn't faded. Ned