oil pressure

ok i just got done swapping a 96 4.o into my 93 cherokee, and the oil pressure light is on (dummy guage) i know that i put exactly enough oil in it. should i replace the oil pressure sending unit? (i heard that they are different for the different guage clusters) or should i just leave it and install a mechanical guage?

Install a mechanical gage. You should also be able to put your old sending unit back in for $0.

ya already got rid of the old engine, so i'm puting in the new guage.