start but wont shut off!
 

working on a 68 plymouth 440 roadrunner. the cars been on a msd box for a year now and never had this issue. replaced the alternator and after this i had this issue. if the other 2 wires on the alt were hooked up backwards could this have burnt something up? but the starter switch is good. i switched it out still will not turn off when key is in off position. but will start everytime. what can cause this?