Can i change a simple product to downloadable product in magento 1.9.3.
is there any option to purchase out of stock, downloadable products
If it's only 2 maybe you should just create 2 new products with same url and change the url of the old ones.
Alternatively you could do some programming.
Maybe start with this class Mage_Catalog_Model_Product_Type_Grouped. the public function getAssociatedProducts returns an array of associated products which you can simply sort through applying whatever logic before creating your new products.
You have to deal with store scope etc during this process but there's lots of tutorials.
and you can create custom product type like this :