273 crank into a 340

You will have to rebalance the rotating assembly. Also, I don't recall the specific years, but there is a chance that your 273 crank has a smaller register for the converter snout than the newer, more common Mopar converters. If needed, you could have the back of the crank machined to accept the more common converters.

I just don't remember what year they went to the bigger size in the 273 cranks.