Its all abit confusing, our MX's were your (American) DT175E, F, G
The prefix is 2A7
They were the monoshock bikes with 6 speed transmission
However from what I understand the American MX's were without some street running gear werent they, lights, horn and the like (not 100% on that though)
The prefix 443 is DT175A, B. As Cynic said it is an earlier bike, (twinshock) 5 speed. The engine will fit I think and for a field bike would be fine, I think that there is a slight difference in the chain run (5mm more outward on the monoshocks) but that shouldnt matter really on a field bike.
However the electrics are different and the early bike runs with points.