Sorry,
The groove is in the crank's "snout", where the old seal "rode" on the snout.
Grinding the cranks means grinding the main-bearing and rod-bearing journals on the crank.
Good luck, and keep asking questions. There are few things so nice for enjoying our trucks as getting a properly rebuilt engine. There are few things worse in enjoying our trucks/hobby than paying $$$ for a badly rebuilt engine.
I'd spend the extra money and get a good/clear warranty in writing. Re-install and test the rebuilt engine immediately upon getting it back from the shop.
