This link is to a chart showing the Letter Prefix ser# system Savage used post GCA68.
It's on Savage Shooters dot com

Though the post teases you with a miniscule size pic of the chart, you have to be a member of that Forum to actually see the full size chart when you click on it.
I'm not a member so I can't say if the info is helpfull of not.
The note mentioning that the chart is a general outline of start and end serial number along with year.
Might be helpful.

Dating Serial Numbers with a Letter Prefix