Per 50.000 maledetti dollari is a eurospy movie (very rare but there are German and Spanish prints), and Tutto sul rosso a eurocrime movie (unreleased to my knowledge).
Una bara per ringo is the non-original italian title for the German/Spanish western Wer kennt Jonny R, available in… German (cut) and Spanish (uncut) prints.
Un dollaro di fuoco is available in French and Spanish prints.
The lost ones are definitely
-Vamos a matar Sartana (prints seem to be circulating, but extremely rare)
-Crisantemi per un branco di carogne
-I fantasmi di Omah-Ri (unknown if this production even got finished)
Every hardcore collector has been looking for Vamos a Matar and Crisantemi for ages, and yes, this topic has come up before