How do you chose what spark plug to use?

[rwest]

My 1977 is slightly modified:

It has Mahle RS P/Cs, SC cams, PMO EFI and EDIS ignition.

Currently I have Denso W22EPR-U which should be a factory spec plug.

Since my setup is now different, how would I know if that plug is still a good choice or which plugs may be better?

Thanks.