Check engine and air bag light flashing on 1992 Ford Mustang LX

recently changed engine from 2.3L to 5.0 in my 92 ford mustang and now I have the check engine and air bag light flashing. When I first start the car it is off, after a minute it begins flashing, the car sounds and feel fine while driving. There seems to be no other problems. I have heard that it could be a module, but how true is this. I am looking for specific things to check for without having to remove this engine and starting from scratch. Any suggestions, thank you?

Asked by for the 1992 Ford Mustang LX
Have you checked the diagnostic trouble codes in the engine module and the ABS module?
I also have a 92' 5.0 gt with the air bag light flashing. I get a code of 34. can anyone tell me where the sensor is?