The issue surrounding the wiring diagrams is that Morgan used the same wiring diagrams for a Plus 8 (which had an externally regulated alternator) and the 4/4 (which didn't)!

The Ford crossflow never used an externally regulated alternator.

Makes sense wiring it to the battery post on the solenoid.

On the crossflow rally cars we used a compact alternator from a Kubota, very light and powerful (60A to 95A) and cheap too - about 75 quid from the local Kubota dealers.

Arwyn