Re: power consumption
One of the problems of the 1978 system is that there is only one solenoid that is dedicated to the "up" side of the system. The down side takes its power directly from and through the switch. Any weakness in the wiring, and it cannot take the load.
The fuse in the PT&T circuit box should protect the wiring and prevent the wiring from burning, so you may want to check to be sure that it is rated low enough to do that.
In the meantime, you could add another solenoid or a relay system to provide the power directly if you wanted.