Radiator hose.

Buy a radiator for a 70 Duster 340. An aluminum radiator like in the link below, with 2 rows of big tubes will cool better than 3 rows of smaller rows. The radiator in the link is the one I plan to use in my 65 Barracuda.

https://www.coldcaseradiators.com/product/70-72-ab-body-17x22-auto-aluminum-performance-radiator