I think the way the flywheel is balanced depends on the engine
I just checked a flywheel I have in the garage. It is an Indenor flywheel from an XDP 4-88 (Volvo Penta
MD19) engine, and it is symetrical in all respects. Symetrical bolt holes, no change in mass anywhere on the flywheel, etc. and it's obvious the flywheel can be fitted in any position on the crankshaft.
I also checked a flywheel from a GM 350 cu.in. engine. No symmetry in the flywheel at all. The mounting holes are not symetrical, so the flywheel can only be fitted in one position on the crankshaft. Plus the location of the mass within the flywheel is offset to one side and not symetrical. In this engine the flywheel plays an important part in the overall balance of the engine and couldn't be readily changed to another engine.
This is something that will have to be considered when swapping the flywheels on your engines.