Why would you want an OBDII swap?
because the obd2 system is "heads and shoulders" ahead/ more advanced/ and easier to tune due to the advanced datalogging options available.
Much better than the EEC IV stuff, which has no datalogging solution.. or didn't at the time.
Tuning an EEC 4 car without datalogging is like "paint by numbers" in a closet with the lights turned off. Your painting of a castle quickly turns into a cactus and you cant figure out why.
OBD2 > EEC IV