To "center" the gauge may be difficult as there is a square cutout that orients the gauge within the instrument cluster. If you have a Dremel moto-tool and a metal cutting bit, you might be able to re-cut that square or do away with it and then re-drill the 2 screw holes but it won't be easy work at all...something to take up time on a cold wet night, possibly.
Jon, It really won't work to reorient that square hole as the needle and number scale are in one assembly. It would just reorient the whole gauge behind the bezel. You may be right about there not being any gears in it as it's a partial sweep needle and might just have a link between the bourdon tube and the needle lever. I haven't looked at mine for a few years. Here's a picture of the gauge and it's mount in the cluster.
