Hi Rishi,
Look out if these pistons have the oil squirt excavation on the bottom rim of the piston, otherwise it isn't advisable to use them on the R. The 200sx don't have these oil squirts. What you eventually can do is to "cut" some material of the oil squirts so that the piston will not hit it's top and still can use the oil squirt. This could be done and is advised by JGY when using 200sx specific pistons, like the CP pistons.
Your CR will be fine, the only difference causing the CR in the R engine is indeed the circle shape of the combustion chamber.
rgds
habib