this is what i am working on right now to lower the rear of my bus. its the first time i have done this and learnt of a how to on the samba.
i will be putting in a 1500 beetle box so i do not have to mess around with flipping the diff after the reduction hub removal
i got 2 long swing axles and axle tubes
i got 2 short axle tubes
you need to make the short axle tube as long as the long axle tube ,im guessing the reason you need the short axle tubes longer is so the shock tower mount will be in the correct position.
started with this

then cut of the base of the short axle tube,figure out what length is needed then cut to make up the difference, i cut mine so that when the 2 tubes are rewelded the axle boot will cover it and will not be seen

i didnt say that the only reason you need the long tubes is for the overall lenght and bottom section as shown in previous pic.

then joining the 2 together check the overall lenght twice then weld it back together.
i havent welded it yet ,dont forget to replace the flange that will mate onto the gearbox you are goint use.
also you need to modify the spring plate to except the beetle axle as i am not up to this point i cant say how to do it