Your factory manual will have a listing for each n every coil and its correct part number. They are usually listed in a Sega manual in the first dozen pages, and usually 2 x pages is devoted to every coil n part number for a Sega.
Also, make sure you rebuild the flipper kits and buy the right buschs as well, level the machine to the correct slope, also in your games manual, and u shld be fine.
If I find any coils have been replaced with different ones, I always replace them with the exact ones from the Sega catalogue.

Alot of people replace them with data east or williams ones because thats what they have on them when they do a hack repair, but going back to the exact part number listed in your games manual is the answer.   Dont try n substitute with other brands cause u will just play around forever and never get it rioght.