I have some KB 237 pistons and want to set new rings, they are bored 30 over what do you all suggest

 

I like the ones they recommend, standard stuff moly faced cast top, cast second and stainless oil.

 

x2. They will spec out ring clearance on the piston sheet. I don't like to stray from the manufacturers specs.

Keep in mind the engine builder should have finished the bores to the rings you specd. Different rings need different bore finish.