Need A Start!

[wblx3]

I Must Be Overlooking Something. My '72 K5, Like New, Has Me Stumped. For A Time When I Turned The Key I Would Get A Pretty Good Bang From The Starter, Not Every Time Though. Then It Got To The Point Where Once In A While When I Turned The Key Nothing Happened, Absolutely Nothing. Now However Nothing Happens All Time. The Ignition System Is Dead. The Ignition Switch Still Starts The Stereo But Thats It. I Thought It Might Be The Battery Cable But An Ohm Meter Proved Me Wrong. Before I Go Out And Buy Some New Parts Are There Any Thoughts Out There. I Have Had My Blazer Since '73 And Seeing It Just Sit There Down For The Count Is Like Having A Sick Kid.
I Put In An Msd Electronic Ignition A Few Years Ago And I Don't Know Enough About It To Know If That Might Be The Culprit.
Heres Hoping Theres An Answer Out There, Bill