When I checked my axle I set the beam up dead level in a vise with a spirit level across the two spring pads side to side. Then I checked both spring pads with an angle gauge front to back -the angle should be the same or close here if the axle is straight. Then I put the kingpins in the axle eyes so that most of the kingpin was sticking out the top of the eyes and checked the angles of these with an angle gauge. Two measurements here - front to back; this the axle castor -The king pins should be at 90 degrees to the spring pad forward and back measurement (the on-the-road castor is set by the spring wedges). Side to side measurement; this is the king pin inclination which will set the camber when the spindles are fitted -can't remember what angle this should be, but it should be the same both sides or within 1/2 degree or so.

Stuart.

1950 Chevrolet 3100 (occasionally working) truck:https://c2.staticflickr.com/6/5490/30684982201_6dc479d18d_c.jpg
1928 Chevrolet AB National Phaeton: https://c4.staticflickr.com/6/5573/30137792083_42886d30a4_c.jpg
1932 Austin Special Sports: https://c8.staticflickr.com/6/5793/30116567183_1520e67c4d_z.jpg