If you remove your balance shafts be sure to plug this hole. It's an oil passage to lube the balance shafts. Dennis used a 5/16" coarse allen head set screw. You'll need to drill the bedplate hole out larger and tap it 5/16" coarse in order for your plug to fit. If you skip this step your engine will die a quick death.
It is also an excellent idea to use the balance shaft mounting holes to locate an oil pan baffle. Gary Donovan was the first person to do something like this, but in a 2.5 Turbo engine for his 10sec Reliant. The balance shaft carrier acts as a quazi oil baffle. Once it has been removed the oil can slosh around quite a bit, possibly starving the oil pump pickup while accelerating hard, braking hard, or cornering quickly. If you leave the shaft assembly in, but disconnect the chain, you still need to plug the oil supply hole anyway.