Syncro 4&4 Discussion and Q&A last answered over 2 years ago.
You may also want to visit the Wiki(pedia) for a more structured index of T25 repair, maintenance, technical and ownership topics (browse for Syncro links)
You can find further syncro specific information on the Syncronauts website.
Getting wheels in the correct ET range is important for steering geometry and good road manners.
Small ET sets the wheel outboard i.e increased track but too little and you'll get unpleasant kick-back through the steering when the wheels encounter obstacles (not so obvious with PAS but worth knowing about)
Ronals were only about ET23 so that must be considered the limit?
You need to consider the actual tyre width along with ET to avoid fouling problems when going large. Rim width not that critical if you're sensible afaik but I'm no expert
I'm running 215/75/15 AT's on 5.5 x 15" ET60 Vito rims with 30mm spacers to get ET30. Clears the sliding doors by a good 15mm. No fouling on locks on or off road. Van not lifted either.
1985 Oettinger 3.2 Caravelle RHD syncro twin slider. SA Microbus bumpers, duplex winch system, ARC 7X15 period alloys