K2543 modification for more current?

k2543 has max 4 amp, but i want to use Lucas dlb 198 coil it has 1 ohm resistance so k2543 sholud be able to resist to 12 amp.
which modifications suggest to it?( replace transistors to more powerful etc… ?)

You will need better cooling and a transistor that can handle the current.
Most likely current transistor can handle the current, but it has been limited to 4A because of the small heatsink.
Please check the transistor datasheet for max. allowable current and cooling requirements.