273 Crankshaft Quiz

The original 273 in 64-65 used a lot of poly 318 parts, including crank and rods, timing cover, damper, pulleys and alternator bracket (that's what the extra mounting holes are for). (Distributors are interchangeable, but 273's had a different advance curve.)

To keep the balance the same, 273's used heavy, thick-walled piston pins to keep the piston/pin weight the same as the poly 318. So using a poly 318 crank in an early 273 doesn't affect balance. Wedge 318's? I have no knowledge or any reason to doubt the comment above that their balance is different.