you have one other option based on what I've read (havn't done it yet, but bought the unit)..... buy the 6AL2 programable, and you don't use any springs and lock down the mechanical advance. The 6AL2 Prog. does all the advancing per the input via a PC link that comes with it. No Moving parts this way.. all done "digitally"
Good luck, Mark
Here's a quote from the MSD 6AL2 Prog. web page
"The new ignition, Part Number 6530, is based on the same output as the 6AL-2, but rather than rotary dials for rpm adjustments it sports a serial port that connects to a PC. Once you load MSD’s Windows based software on your PC, you’re ready to start mapping and programming. To start, you can get rid of the weights and springs that control the mechanical advance of your distributor. Go ahead and lock it out because you can now create a timing curve that allows you to manipulate the timing down to tenth of a degree increments every 100 rpm. The advantage is precise timing control, with the ability to ramp the timing in or retard it at exactly the rpm that you want it to move. Want more timing out for a start retard? Simply click the mouse and move a couple dots in position. Like a high speed retard? Clickity-click!
"