1993 Ford Mustang 1993 Ignition problem.

About 5 or 6 months ago my car started skipping. It wouldn't do it all the time but when it did the RPM gauge would read half RPMs. Ex. It would really be at 4000 but it would only read 2000. Today I was going down the road and the car just cut off for no reason at all. Also when it starts it sputters and the whole cars shakes. Im thinking its the Ignition coil. Ive replaced plugs and wires, air filter, I cant get the codes read anywhere because it's a 1993. Any help is greatly appreciated.