Need pics of Vac. Sol. Switch(1974 258)

I'm in the process of rewiring my engine harness and the one melted wire in the bundle is a 16g. orange wire (a-37). It terminates near the oil pressure sender but the thing that it goes to is missing.
I think it has something to do with the transmission controlled spark but that entire system is not present and I don't know if a PO removed it or it was not on my Aug 74 built 258.
I'm trying to restore to original configuration. Emission control crap and all.
Anyone have any pics of this thing? or any underhood pics of an unmolested 74 258?
The FSM and parts illustrations are a little vague and seem to show a few different systems for differing build-outs