i will say to you that if you have rear droped axles and front drive under the engine is definetly 1501, same as an l185dt.
the l175dt and the l1500dt uses diferent style axles at front and the rear, it also has deferent fenders, etc...
l1500dt version.
while the l1501dt (l185dt) uses this style..
as for the engine is almost the same..
with the 1500 to have the z750 and the 1501 to use the z751.
the age now is not so accurate because noone has info for them.