Yeah totally agree with the above,
IF it's done with a decent modern body then it's fine, but if it's using an old body off an old smiley transit like loads are then the payload won't make it worthwhile
Pretty much like any conversion, just do it right the 1st time and it's all good
I know the payload if mine is just over 1500 kgs, so not to bad
There's lads of fabrication places that'll knock you up a decent new lightweight body for around £1500, so it's not that expensive to do it right (as long as you don't mind doing some of the donkey work yourself)