Help! Drill bit broke off inside engine block.Iv

[Moneypit]

I've got a 305 block that was made somewhere between 80-85(that is as specific as I could get from the casting numbers). The oil pressure sensor was stuck in the block and I could not get it to screw out. I even broke an easy out trying to get it to. So I decided to drill it out. When I made it all the way through with the drill bit it broke off inside the block. I already the engine completely together and getting ready to put it in, just needed to remove old sensor and install new one. So I removed everything down to and including the heads and oil pan and I can see no way to get into the galley in which the drill bit broke off into. Does anyone have any advice on what I should do? Thanks in advance.