Advantages of 300tdi over 200tdi?

The 200 is definitely the simplest and as an upgrade from a td the easiest to fit - the mounting points are the same (whereas the 300 mounts differently to the chassis), the gearbox and box mount are the same (whereas the 300 ideally mounts to a different gearbox and needs modification to mount to the 77 bellend housing) and the 300 has more gadgetry, although is still not significantly electric. The 200 only needs one wire but the 300 needs about 12, but that's\mopre to do with emmissoions monitoring and unnecessary wizardry.

I thought LT stood for Leyland Transport???

All these engines, up to and not including (obviously!!!) the td5 (including all petrol and diesel 2.25 and 2.5's) use the same lump. As such increasing bore would increase capacity, and as capacity wasn't increased, neither was bore (except of course from 2 1/4 to 2.5 where stroke was increased to increase capacity)

Thanks for everybodies help, think the 300 might be the one I have had the td5 in a discovery but wanted something a bit easier to work on and really want a 90 next. will continue to search for one I have sold my car now so ready to buy.
APS90