The crank and rods are the same between the 273 and 318. The 273 pistons were lighter because the were smaller so Mopar used a heavier wrist pin to compensate.
I was under the impression that 273 rods had thinner beams and floating pins (1618669 64-71). Vs the pressed pin 318's (72-91). The 318's I've disassembled seem to have the same rod as the 360 pressed pin. But I may be mistaken.
64-67 273 have a forged crankshaft as well. I hear there are steel crank 318's out there as well, but the four I have broken down where cast...with pressed pin rods.