No spark...

The HEI that some ex owner put in died (no big surprise) so I put MoPar original stuff in & it fired right up & ran good!
So I drove it a little & then left it but next day it started run bad & then worse & then not at all... So I've been trying 4 different coils & tried all wiring but I don't get any spark to the distributor, even messured the lead from coil to ditr. cap & it's fine but ain giving any spark.
When I messure + on the coil with ignition on it's fine but when I messure the minus it shows only a tiny bit of current but when I ohm-messure between + & - onm the coil it's a STRONG connection!
If any of you guys messure your stuff; do you get the same as I do?