I took apart one of the projector units I bought . It consists of the reflector, an aperture and in this case the shutter has a dipper unit which moves an additional light blocker up or down, and the lens holder and lens:
the light field projected is a slot, not a circle. theres not much leeway for error in aiming.
Here's what the (unfinished) headlamps look like roughly thrown together:
there is an additional high beam unit to go in both yet.
Here's the light fields produced when both globes are powered from an old battery charger:
Low beam
high beam: