Is it on the car or out of the car? most everyone uses a 1/2 npt with a -10 drain, some use a -12 drain it just really depends on preference I guess it would make sense to put a 3/4 on there if you wanted a -12 and maximum drain. The hole in the pan looked pretty big from memory so give it a try but I don't know for sure, I think it is larger than that. if its out of the car just get a 3/4 bung welded on if you want to go that big.

 

Well it is a -10AN on one side and 3/4npt on the other.. I believe the factory drian inside diameter is right at 1".. So if this is true the tap won't fit cause its OD is 1.09"

*update* the 3/4 bung for the oil return line is too large its indeed an ousisde diameter of 1.09" witch does not allow you to just drill the center hole out. You will be chunking away at more of the oil pan then I was comfortable with. So, as verified many times before 1/2npt to -10AN is perfect.. Or you can even get 1/2 to -12AN if you really wanted.

 

Nevermind figured it out