596 casting or 308 casting for mild 360 4bbl

My '79 Magnum is listed at (IIRC) 3675.
318/904, ac/ps/pb bench, full spare tire.
I did add weight to it with a '78 "P" code Cordoba's XHD trans cooler, XHD A/C condenser, 727 & (3.55's) 9-1/4 rear. Buckets seats and center console.
I did go back to a small block (5.9) and retained a SB 727 for use.

Only weight savings items are a new aluminum radiator, rpm intake, headers.

The car move well. (Nothing the right cam wouldn't fix! And a good set of heads to allow some more power! )