Possible purchase

OBDI started in '91 or '92 depending on engine family, they still used a crank sensor and were MPI. Early magnums.
Before that they were TBI ('88ish-'91/2ish?)- no crank sensor on flywheel.
Before that there was a weird quasi computerized carb for a couple of years.
I don't know about when Mopar started OBD1 but GM started in 1980. What a mess that was.