I've never really cared for that diagram. I don't use "one wire" alternators, and see no need for a separate starter solenoid, but here's how I'd do it instead.
The problem with the above diagram is:
On a street car, you have to ALWAYS pull the disconnect, or the continuous duty solenoid will always be on
There is a considerable amount of wiring that is not killed by the switch. As shown, if something should short or stick in the start circuit, the starter could be energized regardless of the disconnect
Last, you have to run a heavy charging wire clear to the back and clear back up front to the loads
In the diagram below, EVERYTHING is killed by the disconnect. You use a 4 terminal instead of a "two terminal", nominal cost increase. The solenoid drops out when the key is off.
Mount the continuous solenoid up front instead of in the trunk. This allows a short charging lead to the loads in the car, and only one fairly heavy lead to the battery for charging
You can use #14 or 12 for the lead from the disconnect to the front solenoid coil
You can use # 14 or 12 from the factory start relay to the Ford solenoid coil
You can use #6 or larger from the factory start relay to the disconnect
You can use #"huge" from the Ford solenoid to the starter
NOTE that Continuous duty solenoids are not wired like Ford solenoids. Continuous duty solenoids have two coil terminals (the small) one of which must be grounded. In this case, it goes back through the disconnect
Ford solenoids may have one or two small terminals. Here, you use the "S" terminal, and leave the "I" terminal disconnected
EDIT I sloppy added two diodes, 10 or 20A from Rad Shack. These will keep the solenoid from dropping out until the alternator spins down (when shut off by the key) and will keep the output of the alternator from "spiking."
