It will be less cost and period correct to stick with leaf springs. Leaf spings will have an added benefit of having a longer service life and if you need to in the future the leaf spings are servicable independant of the axle. (NOt so with a torsion axle)
1966 Mercury Park Lane 4 DR Breezeway 410 4V, C-6, 2.80 - Streamless.
1966 Lincoln 4 door Convertible 462 4V 1971 Ford LTD Convertible 429 4V Phoenix ~ Yeah it's hot however it's a dry heat!