As I understand it, the 5 ohms requirement is principally because the points ignition system (true for many, not just Honda) have extended dwell time at low rpm. With 5 ohms allowing longer time to saturate without overheating the coil, you could try pushing the points gap as wide as specification allows, and effectively shorten dwell time to use the 3ohm coils.
It's certainly not a complete balance but could allow you to at least run with them while checking the coils for too much heat.