Need help constructing a mirrored assembly

[luggw1]

OS: Linux Mint 19.3
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.4.
Build type: Release
Python version: 3.6.8
Qt version: 5.9.5
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)

I've attached a model of a set of components I'm using to actuate a switch at one end of a drop section on my model railroad for the purpose of killing power in a section of track leading up to the chasm when the bridge is open. In a second case I have a slightly different bridge configuration where I have to put the components on the other side of the bridge, so I need to model the benchwork (in a new file) and I'd like to use these component models mirroring the SwitchBracket and ActuatorBody and locating them appropriately.

My question is what tools and workbenches I should use to make this happen. On the surface, it seems like the A2Plus workbench would be suitable for assembling the parts, but I don't see a way to mirror a component. Am I missing something there, or is there another tool I should be using to achieve the results I want?

Thanks for the help.
Bill Lugg

[papyblaise]

Use Miror of Part Wb and move it by modify "Base"

[luggw1]

OS: Linux Mint 19.3
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.4.
Build type: Release
Python version: 3.6.8
Qt version: 5.9.5
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)

OK, so here's what I've done to begin to solve this problem (SwitchBrackets-BackBridge-Assembly.FCStd contains my work). As you can see, I've modelled the bridge in question, added it to the assembly and began adding the other components, mirroring when appropriate using papyblaise's suggestion. I've been able to align most of the parts using the constraints of the A2Plus workbench, but I've run into a problem where I don't have two parallel planes I can offset with a constraint.

the orange Actuator-DropEnd (Mirror #1) is a case in point. I need to fix it 1.375" from the end of the bridge, but no plane on the bridge is parallel with a plane on the Actuator. I haven't found another A2Plus constraint that allows an offset. Is there another way to control the position of a part like this?

Thanks.
Bill Lugg