The rods aren't the weak point in the big block, the rod bolts are. Mopar big blocks have very heavy pistons, yet they used the same size rod bolts as the 318. Rod bolt stretch at high RPMs is what causes most spun rod bearings in our big blocks. Chrysler engineers realized this and used larger rod bolts in the Hemi. Get yourself some ARP high strength rod bolts, use lock tight on the nuts, keep your RPMs under 6,800 and your 383 will be a lot more durable.