Transmsn/trans case seal... Help!

[smith]

I was referred to a local shop to have them put a new seal between my transmsn and trans case because the trans case was overflowing and stuff. Anyway I just called to check on my baby and the guy said the part they got from the local chevy dealer wasn't the right one and he couldn't find the right one... Good god. Anyone know the proper name or where I can get one quick. I did a quick look on-line with no luck because I don't know what it's called. Any info would help. The shop is still looking but I'd like a back-up plan.
Thanks