I tried the Cen-Tech and it did not work for me. I ended up going with a Sunpro CP8215 that I got from Amazon. Pretty simple just took the guts out and slipped it in to the spot and put the original face back on.
Curious if you had to stretch the holes out in the housing. When I slipped the gauge into the holes, the needle hits the round center post. I will need to move the gauge up about an 1/8" so that the bottom of the needle does not hit the post.