When I used a Flashforge Dreamer (which is essentially a Replicator clone), one of the issues I had was aligning the nozzles vertically in relation to each other. You only have to be a micro-smidgen off and it causes havoc when trying to use dual filaments.
The following works for any Replcator-type clone (Dreamer, Wanhoa 4S etc).
I resolved the problem by replacing the filament holders mounted on the carriage, using E3D assemblies - the filament drive motors were relocated to the back panel of the printer. Furthermore I could easily remove and maintain the E3D assemblies without having to break down the carriage, so changing nozzles was a cinch.
Maintaining the height of the nozzles was very simple - the E3D assemblies were mounted on a spring loaded bar which could be wound up and down either end at macro level, to make perfect adjustment of the nozzles in relation to each other.
See the Thingiverse project at https://www.thingiverse.com/thing:2675149