i am runing the msd 6al on my 87 iroc with the msd 8876 wiring harness for the gm dual plug coil.. i purchased the msd 8676 module 0-11 degrees thinkin it plugged right into the 6al ignition box...but i found out i had to buy the seperat retard box... im not planing to return the module... so..... is it compatible with the MSD #8982 Start / Retard Timing Control or either the MSD 8680??..is the msd 8680 just to advance timing??...in other words can i replace the 8680 smaller control **** with the 8676 module?? thanks that would help out alot