Select two circular edges instead of the faces of gear teeth.
You can suppress the constraint to rotate the gears to align the tooth mesh then unsuppress the constraint.
@shmbry
Just curiosity on my part.. Did you generate the gears yourself or were these pre-built files? I ask because viewed from one side 'front' the gear meshing looks OK but not from the reverse side.
If you want accurate bevel gears, I think the guide by @Oldbelt is a good starting point. Gear templates
I did it roughly from the works drawing attached. The overall geometery is ok, but I didn't go into the minutiae. There is a pdf online regarding Meccano gear theory, but it's several pages long.
For my immediate needs of verifying the space claim in a bigger project I have created a gear as a blank with its periphery at the PCD. The notch is to visualise the gear constraint. The geometery of Meccano gears is known and proven so apart from an interesting CAD exercise ...