Bad Master Cylinder or Air?

You have air. If you had the solid plugs for the M/C, it should bleed and get a very solid feel. Some M/C's used to give solid plugs for bleeding, instead of hoses looped to the top.

I used to see an abandoned 73-74 Road Runner on the way to Keymar from Taneytown. My old green Fury wagon is out there somewhere too.
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If the 73-74 Road Runner your talking about is right along 194 it's still there...