Lots of help received here from kind souls NJ Sal, Stew, Stromberg-Kevin, et. al..
Long story short, found the short (doh!), and was able to power up the Mk. III for the first time today.
It's got a ways to go for break in, but it biases, and is now pumping out tunes in glorious mono-phonic sound.
I can't thank enough all those who lent their time/expertise.