umm I guess you could run the + and - wires from the internal coil to run the external coil, get a USDM h22/23 cap and rotor as well as your aftermarket coil..
or
I think you can get an external coil conversion kit for a civic or Accords ( 91-92 again, likely the same kit if one is made).

BTW I don't think that running a bigger badder ignition is going to gain you any fuel mileage back, it doesn't hurt it but I can't see any gain in mileage unless something has gone bad. have you changed plugs yet? I'd try that first if it isn't running well.
Is your car giving you the check engine light?