I have an 80SC and I installed and MSD 6AL ($250) and MSD Blaser HV Coil ($50) and Maganacor leads ($170). With new plugs, rotor and a larger gap, you can certainly feel the lower end power difference (below 3500 rpm) it is really quite substantial over the stock CD Box config. I though it was one of the best upgrades I've done to my car! Great bolt on upgrade that can be simply restored to stock if you ever want!
Wayne's got this in his 101 Projects book, or here
http://www.pelicanparts.com/techarticles/mult_MSD_install/mult_MSD_install.htm
.Steven
1980 SC