12 v coil

Oh dear the BOYER BRANSDEN system on a twin uses 2 off 6V coils preferable (but you can use 2 off 12V coils) The coils are connected in series. There is NO ballast resistors. The term 'coil pack' has no meaning for a Norton Twin..

What kind of Boyer ignition?

It should be written on the ignition box.

I would ask Alan Osborn to clarify his wiring circuits for both coil applications to ensure a successful outcome.

Does your bike have contact breaker points?

What model and year is the bike?

If this bike is original it will have an 18D2 distributor run on 6V with a single 6V ignition coil.
If for any reason it has twin coils (preferable 6V but maybe 12V) then it would be running a straight forward electronic ignition -ie modified 18D2 or even some magneto replacement housing with the Boyer or similar ignition inside. There is NO need whatsoever for any Ballast resistor or ballast type coils.

That Boyer Mk 3 ignition is meant for two six volt coils wired in series, or one dual HT output twelve volt coil.

And no ballast resistors.

Is there a trigger mechanism in a housing that takes the place of the old distributor behind the cylinders?

Looks like there is.

All good.

They look suitable to be used as a pair in series. I haven't tried them.

https://www.trispark.com.au/collections/ignition-coils-ht-leads-and-more/products/6-volt-ignition-coil-lucas-style

Do you have Boyer instructions?

The coil should have a mounting bracket, if this done up correctly then it will not come loose. I cannot see why you need special Trispark coils on such a basic machine? The crucial thing here is the Boyer MKIII, this works with very traditional 6V coils as fitted to Commandos and Triumphs, they come in a Lucas box (made in far East sold by the Wassel empire)