the casting number on rods should be 496, last 3. theses are the good stock rods. I retired my set after 1800 runs in my 340, with stock weight pistons and trw lightened to match. these were ran up to 7000 rpm in the traps, 6500 shifted. only work done was new bolts every 5 years,( mopar bolts) ARP wasn't around yet. never broke a 496 rod. BTW, this took 18 years to amass 1800 runs, to resize rods cost $ 90, plus bolts, way less than new rods. nothing wrong with those rods!!!!