Go to a motorBike wrecker or swap meet, floating secondary (double ended) coils are common on four cyl 4 stroke & 2cyl 2 stroke bikes. (newer bikes would be lower ohms due to elect. ignition, I like the old stuff better)
You didn't mention what drives your coil primary, points ?
Important !! When replacing your coil, get one with same or close primary ohms or use a series ballast resistor.
Parallel ignition coils:
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If you try to drive 2 coils (with half the total ohms of original coil) your points will not last as long. (Maybe use 2 ballast resistors.)
Also the 2 coils in parallel would likely "fight" somewhat in resonance, but then try it & see what happens.
There is plenty of resistance in the primary to enable reasonable current sharing as long as the 2 coils are the same as possible, Any problems would be when the coil is in flyback mode & the coil(s) is resonating.
(often things can work well with the "try it" & see aproach)
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Series connection:
Using 2 identical coils (eg: bosh epoxy potted - should be better matched than 2 old oil filled coils)...
You could try connecting the 2 primary in series, don't see why this wouldn't work, as long as the total primary ohms is similar to original.
There would be some interaction between the 2 coils but I dont think it would be significant.
If I had 2 identical coils handy I would give it a test
Tonig.au