Lots me completely, the Bump stop English V elsewhere is just a secondary impact shock absorber. Rubber spacers between springs are sound and impact absorbers.
Raised metal blocks betwwen the chassis is based on low and high variant models such as a raised camper or in the NAFTA models on Tins for allowance of 16" rims as opposed to the normal 15" rims
At the same time a 4x4 of which is raised as to center of gravity,as to ground clearance. same as a 5 metric tonne Cab over chassis variant refereed to as a 616 cdi.
If I look at what you have asked for ,you state 4.6 T this unit is a 5.1 MT unit, down rated to 4.6 MT [OR AS DESIGNATED ON YOUR SPECS A 4.45 TO 4.95 mt VARIANT] with dual rear wheels, with multiple parabolic springs under the SAA codes your main spring will read 903 3200 1850 three designated codes for springs;= X 004 070928 as an example
Your rear main parabolic spring on the eye shackle has a MB number stamped into the actual SPRING IT'S NOT REMOVABLE AS IS THE PRINTED NUMBERING SEQUENCES AS TO CODEX ON THE FACE OF YOUR MAIN PARABOLIC SPRING. it-represents the loadings as to your front axle it should read 1850 on a Tin cargo van or 1900 KG on a Cab-over chassis unit.
Again your question asks down-rating to 3500 ,unless its a Cargo van single wheel job this model 4.6 can not be configured by down weighting to a 3500 KG unit,unless you can get a certificate from the TUV that the van is used for non commercial use, and it's for private or passenger use only.
You can swap over rear springs to two as a 3.8 GVM /variants one raised the height,with softer ride Or the other is for a lower ride designed to be firmer and carry a higher weight.
ON the Tin ,there was on H/D parabolic single spring that up rated the GVM capacity to 3.8 GVM, and the Compliance plates still remained 3500KG.
Are you looking for a tax plate compliance get out of ticket! or attempting to bring a 4 /5 series van back to 3.4 GVM to get out of the stricter emission controls applied to a 3500.5KG and over van.
I don't think you can do it with out a rectification from an engineer ,if you succeed then a new plate is designated as to the GVM ,now days its a transport approved yellow sticker stating it's new certificated weight.
One member in the UK has a 4.2 GVM SuSi super single wide rear wheel unit van that has a re-certificated plate back to 3.8 or 3500KG variant.and this is a current model 2010 NCV.
Richard