1.6 GTI Coil

Can enyone help!
I have a 1981 1.6 GTI, I've just changed the old ceramic fusebox for the newer spade type fusebox which ment for the later 1.8. I'm not sure if the original coil is man enough to trigger the new fuel pump relay properly.
Car starts and runs, but when it's warmed up engine runs very lumpy, at low revs and the fuel pump relay is constantly clicking.
What confuses me is new coils are advertised separately for 1.6 to the 1.8 but resistance is are the same at kOhm 4.745 and Omh 0.755

Does anyone know the reasons why the coils are advertised separately?
                                             

Edited 04/07/2024… The day after your post I spent 20 minutes typing out a comprehensive reply to your query, including pointers on which coil you needed.

Today, 40 days later your profile shows you've yet to sign back in.

If you ask for help, have the courtesy to at the very least check back for replies / not waste their time… a very poor way to treat others.