LC in a AC Crank Casing?

Hi i recently broke the rear caliper of the engine casing which was near enough unfix-able.

so i went and bought another crank casing which is for air cooled heads but ive read on a different post that its possible to make it liquid cooled.

so im going to run a electric pump use my magnito side of the crank casing with the AC left side of crank case

but even tho the hole for the water pump has been blocked off the water pump belt from the crank goes over the cog for the water pump but it also goes in the back of the oil pump

my main question is if i cant use a water pump on the ac casing then how does the bit that goes in the back of the oil pump still spin???

 

There should still be the shaft (as you always need the big cog and the belt even just for the oil pump) but it just won't have the water pump on the other side.

Need to swap everything basically if I remember

 

Thanks for your reply,
There's a shaft there (which doesn't spin like the waterpump 1), but the centre of the cog I got isn't circle its got 2 flat sides which goes over the waterpump shaft, maybe if I buy the genuine AC cog? Maybe that should work?