Add /post_replacements.json, /posts/1234/replacements.json.

app/controllers/post_replacements_controller.rb

@@ -0,0 +1,11 @@
+class PostReplacementsController < ApplicationController
+  respond_to :html, :xml, :json
+  before_filter :approver_only, except: [:index]
+
+  def index
+    params[:search][:post_id] = params.delete(:post_id) if params.has_key?(:post_id)
+    @post_replacements = PostReplacement.search(params[:search]).paginate(params[:page], limit: params[:limit])
+
+    respond_with(@post_replacements)
+  end
+end