does anybody know where I can find a engine wire harness for my 1966 bonneville?

If you are able to get a wiring diagram, it couldn't be too difficult to just make one.
If you care about using the correct color and gauge wires, you could spend a lot of money on wire.

Honestly, shops that specialize in car electrical problems make new wiring harnesses for a reasonable fee. That's not a bad option when you're dealing with an older vehicle. Check these guys out for example: http://www.americanautowire.com/FactoryFit.html

_________________
PontiacDad at WCBF `08: "By any chance, was his name. . .Radomir?"

R.I.P. 10/31/15: 1997 SE: "Silver Shadow"
`05 Mercedes S500