The C3AE-C rod like the later CJ rods can have 2 bolt sizes. 3/8" was the more common 390 small bolt rod. 406 and 427 were the larger 13/32" bolt hipo rods. Same rod forging just two different machining protocols. These were used from 63-65 but work just fine in any FE with a 3.78-3.98 stroke crank.