1973 914 2.0 Pistons, Domed or inverted dome? Options

[szcesuil]

My father-in-law is rebuilding the engine on a 1973 2.0. The repair manual mentions that the pistons should be domed. However, the actual pistons have more of a dwell at the top. If the pistons and crank shaft were replaced at some point, we aren't sure what would be the best way to move forward. Should we use the same type of pistons that are in there or go back to what the factory originally used? If we revert back to the factory domed pistons, would we also need to replace the crank shaft?

Thanks,
Paul