The biggest 8-speed cassette I remember seeing is Shimano Megarange 11-34. Claris are rated for a 32 bottom which means they could probably eke out a 34 but no one should tell you it will definitely work.
Not sure you need the NW ring or the chain catcher on a road bike.
I feel like replacing the RD and the ring and the cassette and the chain and the tires and maybe adding a catcher is going to cost a lot in comparison to the Claris-level bike itself.
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Genesis 49:16-17