How to fit lego power function LED lights onto cargo train (set: 60052)
The cargo train (60052) is not out-of-the-box able to be converted to using LED lights. The light bricks (1x1 round bricks) are fitted on the front bumper of the train with no space left for the light plugs. You would need to make modifications to the train to embed the lights - for example by mounting an additional light on top of the train, or by putting different lights on the front bumper. But you would need special transparent headlight (aka Erling) bricks for that - part 4070 or 30069 is typically used in other train sets.