The fuel servo installation has been fun. I ended up doing a fair amount of research, and even bought "Aircraft Fuel Metering Systems" from Aircraft Technical Books
to make sure I knew what was going on here. Here's a nice drawing I found. From the schematic you can see that the manual mixture control arm is nearest the fuel inlet, and the throttle is near the safetied end nut of the fuel strainer. Thus in the figure below, the throttle has the idle mixture adjustments. The mounting brackets for the control cables are the standard kit from Velocity, but it was a little unclear whether it should go under the servo flange or not. So, concerned that I wouldn't get a good seal that way (see picture below), I decided to mount it on the bottom side.