Hi Greg,
I checked my '68 Service Manual and found the fuseable link on the '68
Wiring diagram for a barracuda/valiant. Looks like it is somewhere on
the Red 10 gauge wire coming off the Starter Relay B terminal. The wire
heads from the relay to the firewall J terminal on the Bulkhead.
(Bulkead, J terminal is Middle set - Bottom right, Or Middle Set Top
Left, Cant tell from the diagram which way it sits on the firewall.)
Its funny, its in the wiring diagrams, but it is no where in the
Electrical trouble-shooting section. Will look at my '68 Satellite in
the morning and see if I can see where it is for you.
--Tom