Crankshaft Casting Numbers

[1990new]

Anyone know the complete story on the crankshaft casting numbers.
The new short block engine I just bought has casting A301.
I just pulled the bottom pan on Rosie tonight (12/29/1991 build date) and the casting is B301.
Both are the short nose crank.
What is the purpose of the casting number?

[1990new]

I found this that someone had posted in a spreadsheet about crankshaft castings but still don't know what it means.
4 cylinder engines
80 cubic inch 1.3 liter
A301 1992-93 3.307
B301 1988-97 3.307

The 3.307 is under a column labeled 'stroke'

Wonder if one is cast and one is forged?

[1990new]

I got confused and I was wrong Both the crank in Rosie and the new engine crank reads A301.
But it would still be nice to understand this.