To align the rear wheel in the swing arm I use a builders 50cm long laser level against the side of the rear wheel tyre and shine the laser beam to the front of the car. On the lower edge of the rear face of the centrally mounted number plate I have some masking tape with 1cm graduations equally spaced in from both ends as the laser dot target. If you place the level on first one side of the tyre then the other and see where the dot sits on the target, you can reposition the axle to get the rear wheel running in alignment with the chassis.
You could improve the accuracy by putting a spacer on the levels edge to make it rest against the wheel rim rather than the tyre but it seems to work OK. Rotate the wheel and re-check the alignment stays the same.
