I have not got the wiring diagrams for the early cars. But I may be able to help a little.
The two wires (one red with a green stripe and one green with a red stripe I think??) on the antenna are the up and down positive feeds to the antenna one is for up the other for down.
The negative for the antenna motor is via the antenna earth strap that is just under the wing. Make sure this strap is connected, making a good earth connection and not rotted away!
Trace the same coloured wires that come out the antenna back to the relays. The microprocessor wires at the relay should be smaller than the wires from the antenna, the up one is white with a black stripe and the down one is red with a black stripe. (I think.)
There should be a black wire going to both the up and down relays for the negative that again should be small and the same size as the microprocessor wires.
So by a process of elimination the third thicker wire to the relays should be the constant power feed. I do not know but I would not be at all surprised if this was a brown wire with a red stripe, but I could be wrong.
Make sure there is a constant 12v on this power feed wire.
My guess is that there is not! (But it is just a guess.)