The drop arm (Pitman arm?), IIRC, is cast iron - if it is in any way different from factory shape, throw it out. I would also be wary of damaged bearings on the sector shaft - if the hit was hard enough to mangle the Pitman arm, I'd be surprised if the box survived intact.
BTW, I just looked at AB website - D2 arm is different from D1/RRC:
This is D2: https://www.roverparts.com/Parts/QJF000030G
This is D1: https://www.roverparts.com/Parts/NTC9235
BTW, I just looked at AB website - D2 arm is different from D1/RRC:
This is D2: https://www.roverparts.com/Parts/QJF000030G
This is D1: https://www.roverparts.com/Parts/NTC9235