Relations, part features, assemblies and save as copy

Greetings all,

I often design similar items. I often design in an assembly and associated features of one part to another. Then, I save as copy of the parts and assembly and begin to make modifications to the new design. But, the features in the new parts are related to the old parts. I find myself deleting features because I cannot figure out how to modify the relations. I just realized when writing this, I should probably open the new assembly and simply replace components. But I'm looking to get educated on how to modify the relations

Thanks for the help in advance.

SolidworksParts And Features