Welcome to T&B Forum,
ray4one -
Renold.
If you are hauling from forests you might want to consider a 4x4 such as a Bedford MK (ex-military) like this:-
http://www.truckandbusforum.com/gall...ge.php?i=24927
and converting it to pull a semi-trailer.
Otherwise a 6x4 with diff-locks as a rigid.