I found this, although the listing for this particular one does not include the 3 litre.
I'll have a look at mine and see if there is something like that on my oil pan.
If indeed there is supposed to be one and yours is leaking, I would say they over or undertightened the bolts.
Maybe they distorted the oil pan ???
And if it's a crate engine, didn't it come with its own oil pan, seems odd ?