Radiator overflow bottle

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G'day, i hope this makes sense to everyone, I'm putting a 1uz into a 40 series landcruiser and originally the radiator had an overflow bottle ( i think thats what its called) with a small plastic cap on it and the radiator had the cap you have to push down and turn to seal.

My question is what did the motor originally run and do i have to run this setup? Or can i keep my original radiator setup?

Cheers,
Adam.