i have heard a lot of positive feedback on the msd ignition system. i plan on installing one in my 75. any one have any pros or cons to these units and can one be installed on my 90 or would it screw up with the computer?

I had a local shop put an MSD Opti-spark in my LT-4, the unit was not putting out enough voltage so they put in an Accel unit.  It shouldn't mess up your ecm.  Summit told my shop that they had several of the MSD's that were junk.  Just what I learned, thank GOD you don't have an Opti-spark.  Regards-Phil