Neutral Bar in junction box

[Franklin]

Can I install a neutral bar in a junction box?I have to relocate 4 panels to a new location approx 50’ away. I must junction box all of the branch circuits and extend them (splice) to the new panel location. All of this is in the job specs. Non of the existing neutrals are identified, so labeling the extensions would be pointless and tracing out every neutral is impractical. There are 4 panels, full  with 42 circuits.

Thanks