The one on the left doesn't look like the ones I remember looking at, not wide enough on the beams
All the 1970 and 1971 "six pack rods" I've seen, had and held and look a lot like the street hemi rods but with 3/8 bolts instead of the 7/16 bolts, not like any of those in the picture . I used them in several original motors for stock rering, cam and lifters and valve job rebuilds.
On any and all my Hi Po serious builds I use new after market longer forged steel I beam or H beam rods with the 7/16 bolts