I believe it's a mark 6 on a T plate, if the indicators on the front are clear (not orange) then its a mark 6. The standard TD that was put in vans makes 75bhp and the TDI from other cars made 90bhp. With the non turbo making 60 it doesn't seem worth the trouble of swapping it for the TD, only a 15bhp gain.
The TDI is much more tunable too as it has a bigger turbo and fuel pump, people do get 170bhp out of them!! although 150 isn't too hard to achieve if you use a FMIC. Having the intercooler above the exhaust and turbo isn't very clever