Name: Rolf Mertig (email_not_shown)
Date: 12/20/17-10:59:10 PM Z

this can be done using "Uncontract" and the option Unique->False.
Adding FCE for abbreviation this
FCE[Uncontract[LC[u, v][p1,
      p2], p1, p2, Unique ->
      False] /. {$AL[1] :> s,
     $AL[2] :> a}] /.
  LC[a, s, u, v] :>
   LC[u, v, a, s]

evaluates to
FV[p1, a] FV[p2, s] LC[u, v, a, s]

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