As above, any sprinter starting with a ‘3’ – 308, 310 etc, the 3 indicates 3.5t GVW and the other two digits are an indication of the engines output – the bigger the number the more sprinty they are. So anything (at least any panel van) with a 3 and MWB or shorter will do the job. What you need to avoid is anything with a ‘2’ (208 etc) as these are between 2.6 and 2.8t which even with a SWB is only going to give you 600kg or so of payload (after fuel and driver)
4XX and 5XX are all more than 3.5t and into tachograph territory
If its borderline don’t forget that anything added after it left the factory isn’t counted on the curb weight so bulkhead and ply lining (and a tank of fuel and you and your two burly mates) etc aren’t factored in