Assuming you are talking about a Model T coil… if the points close at the time of firing, you can use a buzz coil for each cylinder. This is how I run my early Evinrude. You can’t fire more than one spark plug at a time unless you open up the coil and separate the secondary from the primary. (The contact on the bottom of a Model T coil is common to both windings).
If the points open at the time of firing, it can be done but you need a relay for each coil so that the coil fires when the points open. The problem with this arrangement is that there is a lag, so you can’t do this with something that turns really fast. I’ve done this with a Caille RBM, and if you search this site you’ll find the wiring diagram.
If you need to run an opposed twin on a buzz coil, you can set up a set of Model T points at the end of a Zephyr coil. This is how my battery / coil box is set up. To run a single cylinder motor, I ground one side of the secondary leads to the same lead that attaches to the engine, not the one that goes to the isolated point. To run something like a Koban, I can run separate leads to each cylinder instead of grounding one.
If you have a motor with rare, bad coils and the primary is good, you can strip off the secondary and mount an OMC coil anywhere on the motor. Hook the primary wires from the OMC coil to the primary leads of the one in the mag plate, then a high tension wire from the OMC coil to the spark plug. It’s not pretty, but I ran a little Mercury like this quite a while ago.
T
.
.