Hello,
It is very difficult to indicate a value once restored but rest assured the valve of 40 series trucks seems to creep steadily upwards but ultimately it is all about and willing buyer being around when you want to sell.
However with the Troopy very few people will want one with the two long rear benches as most will want to convert it to some form of camper which could work against you if they are the willing buyer as they will then have to add in the conversion costs.
I think this is a difficult decision, even though there as a number of 40/Troopies touring the world, by the time it's restored and converted to a camper, the potential buyer could buy a newer fully converted 70 series for less money.
Much as I and many others want to see every 40 restored, if you are looking at this as a commercial venture, then IMO the margins involved would be quite small.
Regards,
Rodger