[cflsystems]

I didn't keep the changes and my version is 4.2.1
If you insist on changing php files... open xcart_root/product.php find

$smarty->assign("location", $location);

and add before

$new_product_title = $product_info['manufacturer'] . " " . $product_info['product'];
$smarty->assign("new_product_title", $new_product_title);
 

This will create a new variable and won't mess up with the product array. Then use it in product templates where you want the new title to appear

{$new_product_title}