The Ve versus pd power delivery is somewhat different and will be tiresome in the van, you will have to work the gearbox quite a lot ! The ve has a much broader power curve, the pd will break traction easily as the power comes in one big lump ! As Sam mentioned above, a bigger turbo from this day and age with larger injectors will take the 150 PD ARL to over 250 Bhp however you will need to throw some rods in there to stiffen the bottom end.
I will not be that keen on ARL, and probably look for a stock pd130, they are a bit more reliable and don’t wear cams as quickly as the ARL does. Injectors are expensive however Gibonta, Firad, Bosio, and a few more cater for the old pd lump- getting someone that know to set them properly is another matter... Keith at United diesel has experimented with larger nozzles, also Darkside can advise you and probably sell you updated nozzles then there’s only the mapping side of things to massage !
You will need to get a decent billet cam in there, new cam shells, later PD Black tappers and almost every bolt is a stretch bolt ! You should also take the sump pan off and swap the rod bearings bolts if you keep the bottom end stock, it will be cared for if you swap rods though ! Look at ARP hardware.
If i am pedantic I would rather keep tuning the old VE lump, a 11mm pump, better turbo and larger nozzles should see you past 250 Bhp especially as you’ve done the legwork ! Good luck in your quest for more power ! Why not sell the van as it is and just start fresh ? I know it’s challenging to find a rust free t4 nowadays but one from Italy or Spain should have little to no rust ! I am tuning a 2.5 tdi syncro for a tuning shop in my town, it’s a 150 Bhp AXG engine, should go pretty well after the upgrade. Power target is 280 Bhp...