Black Buck's physical and psychological effects

Could Victor tankers have replaced Vulcans for Black Buck if Argentina had waited?

No; Victors could not simply substitute for Vulcans, and Black Buck's strongest effect was psychological rather than runway destruction.

Victor tankers could not take over the Vulcans' Black Buck role in the proposed later-war scenario. Continued Hercules operations at Stanley underpin a skeptical assessment of the raids' runway damage. The raids still imposed substantial psychological pressure on Argentine forces. On this interpretation, that pressure accounts for much of their value despite limited physical damage.