I've had a S2a and a S3 so I'll jot down a few of my recollections...
The 2a was a petrol. It was so quiet you could barely hear it at idle and ran like a little sewing machine on the road.
The S3 diesel on the other hand... @ 30mph you had to shout to have a conversation @ 40mph it wasn't worth trying.
Running costs... the petrol was cheaper to run than the diesel. The diesel was more torquey but they are both pretty gutless in all honesty.
Diesel topped out at 45mph and the petrol topped out at 55ish. An overdrive would have helped in both cases.
A truck cab is MUCH warmer than a van top but feels pretty claustrophobic.
2a's wing mounted wing mirrors are next to useless.
You can't see anything out the back of a truck cab with a tilt fitted on the back
OEM spec headlights are like candles and the beam pattern seems very odd on a 2a due to the lights being so close together and of course the floor mounted hi/lo beam switch takes a bit of getting used to.
If you're any bigger than about 5'6" there won't be anywhere for your right knee and you'll probably get cramp in your right calf anyway as the throttle pedal is in such an awkward position.
Think of a series as a road going tractor. The ride is... harsh... to put it bluntly!
A 200tdi swap is quite common. If I had another (and I would have another) I think I'd certainly consider going that route?
Parbolic springs can be purchased which will help with the ride comfort a little.
Can't think of anything else for the mo!