use the 18rg oil pump for extra capacity
use 18rc drive shaft for the oil pump (note this shaft is shorter than a normal 18rg drive shaft) use the 18rg little plug thing that goes in the block at the top and the associated little gear that sits inside the plug.
now because you use an 18rc drive shaft you won't be able to put the little gear on the front of the timing chain gears that runs the distributor.
as such you need another way to spark the engine.
so set up a hall effect Ignition triggering system by using magnets in the crank to get a signal, do you know what i mean???