Automator Rename Files Sequentially With A Twist

I have batches of files that I need to rename sequentially - easy with an Automator Workflow...*BUT* my file batches have TWO of each item seqentially - they're images of the same item, so essentially I need to rename this way:

image001.jpg -> image001 A

image002.jpg -> image001 B

and xx002, xx003 and so on, each with two versions of the same number in the sequence. Any tips? Thanks!