(mesh guff here, place the needle sepeartely) add_animation 45,0,0 source: speedo, mode: x-rotation
replace 45 with the tach's full swing in degrees, off the top of my head i'd estimate it to be somewhere around 70 degrees, merry christmas.
also what i do is i model the mesh and needle/plunger/stick/whateverthehell solidly, then move the mesh so the origin point is central to the fulcrum of what animates, and then split the mesh into two bits. that way you can place a bigger mesh more accurately and slap the same coordinates onto the animated thing and have it line up without hassle