Not necessarily, I have 50's and 60's rods done all the time. I'm good with Mopar metallurgy from back in the 60's and 70's. I'll report back the cost of the next set of rods I have done. I'm taking a set next week. I have never bought new rods of any kind for my engines, except for my brothers 289 and those were 289 K motor HD Ford rods to replace the diminutive 5/16 rod bolt forgings. First thing is the stress, 2 barrel Chrysler 383, probably never had any stress on the crank or rods. 383 forgings are good. Time is not what matters to a rod forging it is cycling and the stress during the cycles. How many miles do you think are on those rods? The OP is getting ready to build what is in my 68 Formula S 383 right now. Two barrel 383 out of a Chrysler Newport, I just replaced the rod bolts with the Direct Connection rod bolts. Been in there since the 80's and beleive me, that 383 was never babied with a Comp Cams 268 duration and a HP 400 intake and TQ. The original 383 is on a dolly still waiting it's turn. You are right, the rod big end diameter is crucial to having a short block live along with adequate oiling.