The D'Arsonval Approach
If
you're building a sim based on a smaller general aviation plane like a
C-172, you might also take a look at moving coil or D'Arsonval meters.
These are the typical meter movements used in voltmeters and audio
systems before LCDs and LEDs came on the scene. Although they can be
manufactured to move a needle through a 270 degree arc, most such meters
are simple 90 degree units. These meters offer a simple approach to
simulating the fuel quantity and battery current gauges often seen on
the smaller GA craft.
D'Arsonval movements form the basis for VOR and glide slope needles, as well as things like the "to-from" flag on the VOR. These meters tend to be rather delicate, but if you're steady of hand, you might consider adapting the basic movement to a simulated instrument. The units pictured above both have zero on one side of the scale. However, occasionally you will find one with zero in the center, making it a good candidate for just such a project. These meters were picked up at a swap meet for $2US a piece. Similar units show up in the inventory of electronics suppliers handling surplus at prices ranging from $3US to $12US.
D'Arsonval meters can be easily interfaced with micro controllers running pulse width modulation software. You won't need a buffer amp as the meter movements are quite sensitive.