Customize Theme comment template to Insert VoteUp and VoteDown buttons

I am using a theme that has an okay comment template that I would not want to change. However I just want to insert voteup and votedown button directly below the User avartar

ul class=comment-list
  ?php
     wp_list_comments(array(
         'style' = 'ul',
         'short_ping' = true,
         'avatar_size' = 70
     ));
  ?
/ul

I saw a suggestion to add a callbackfunction that would create a new theme. Using this SO here.

 ?php
     wp_list_comments(array(
         'style' = 'ul',
         'short_ping' = true,
         'avatar_size' = 70,
         'callback' = custom_template
     ));
  ?

Then I write my function

  function custom_template ($comment, $depth, $args){
   ?
     // Here goes my custom template
     // I rely want to maintain the present structure and simply add voteup and votedown button
     // Avatar -- Date -- Edit form -- Comment content -- Voteup and Votedown -- Reply form
     // I would style the section to suite my needs
   ?php
  } 

How best can I get the structure of the current form? Or can I use another method without using a callback function which I would need to enqueue or add to a helper function on my plugin?