You are going to need to go backwards a bit and fix it. No biggy......
We all have been there. Roll up your sleeves and get after it.
If it is not correct, just patch the pan and relocate your drain in a different spot.
Also make sure your Rotating Assembly is not in the way if you need to relocate it.
I would seriously consider fixing it with the pan installed. Dip your drill bits in GREASE before you start the drilling to catch the shavings, then after you are done pour oil in the drilled hole I would then fill the pan with about 7 quarts of CHEAP OIL and then let the drain go, call it done.
If you are using a Weld in Bung............ Disregard the instructions above, don't want you to BURN your car to the ground.
This is why they call it Hot Rodding!!:D