[speedfreq]

This is what did it for me. Finally figured it out after a while of playing around...

changes made in /modules/Upselling_Products/related_products.tpl

{$product_links[cat_num].extra_fields[1].value}
{$product_links[cat_num].extra_fields[2].value}{$product_links[cat_num].extra_fields[3].value}

Those will list the first 3 extra fields values. If you want the field name I believe you sub in "field_value" for "value". You can also use a variable in a loop such as something like this:

<span>{section name=field loop=$product_links[cat_num].extra_fields}
{if $product_links[cat_num].extra_fields[field].active eq "Y" && $product_links[cat_num].extra_fields[field].field_value && $product_links[cat_num].extra_fields[field].service_name eq "SHORT_DESC"}
{$product_links[cat_num].extra_fields[field].field_value}
{/if}
{/section}</span>