... Also, the 273 cranks were supposedly forged 64-66. There were also some 318s that came in trucks with forged cranks.
The way to tell by looking, besides knowing the casting numbers (which I do not) is to look at the casting or forging flash on the throws. On a cast crank, the casting flash is 1/4" wide; forged cranks have a 3/8" to 1/2" flash on the throws...