The above info is spot on from 362bkr. H&R prove two springs in the 40mm range, A light duty and a heavy duty. IE 29270-1 or 29270-2.
Of course this can be a mixture of the two spring types for the front and the rear:
Light duty front and rear = Kit 1.
Heavy front and light rear = Kit 2
Light front and heavy rear = Kit 3
Heavy front and rear = Kit 4.
The springs will only be labelled with -1 or -2, not - 4 as that is the kit number on the box not the spring number.
The cross over on the front axle is 1501 kg. So any thing under is a light duty spring, anything over is a heavy duty spring
The cross over for the rear is 1560 kg. Same applies.
We would however not recommend fitting an underrated spring compared to your vans axles weights which is easily found on the vin plate on the left hand side in the engine bay.
This can appear to give a "softer" ride, however, there is no warranty with H&R, the vans status as a T30 for example is void and it may also stress the spring into a failure.
We always recommend to the fit the correct load rated spring for the vehicle unless it needs an increase in spring rating for say a full camper conversion on a T26. Then you can fit the heavy duty rear spring to compensate for the extra weight.
Alternatively, you may also want to consider a spring that offers comfort provides the correct spring rating for the van and has adjustability in ride height on the rear. That would be the Eibach comfort adjustable spring which works really well for campers especially due to being able to adjust up and down depending on the weight of the conversion which is mainly based at the rear of the van. Also TUV approved and suitable for use with original height dampers as long as they are in good working order.
Stay safe, team Chilli.