Ignition switch?

[kmead]

Your ground cable from the engine to the frame needs to be replaced or upgraded. It it likely why those wires burnt through at the oil pressure switch.

I have one that runs from the engine mount where it attaches to the block and then goes to one of the bumper bolts (I have an older car which has non absorbing bumpers). Other alternative mounting positions could be the mounting for the alternator or the oil filter mounts.

The OE one is a braided cable that runs from the transmission to a transmission mounting bolt as I recall, they degrade over time and often are disconnected by previous owners.

[70spider]

Update.
I had a good stretch of weather the past couple of days and seemed to have found the issue. Now don't laugh when I tell you what it was. It appears the PO had done some fancy wiring, shortening the wire that leads from the alternator to the battery to the point it barely reached, as it so happens this wire was considerably loose at the post connection. With this it appears that the battery wasn't getting charged. I charged the battery, secured the alt wire to the battery, and away I went and is running good. I feel so stupid thinking it was the ignition switch, an unfortunate consequence of thinking the glass is half empty personality. Sorry for the false alarm, but the info was great so when I do have an ignition switch issue I will know what to do.
Thanks Pesto

[124JOE]

the sipa switch is rebuildable

edit;my spider left me stranded twice

once was the points welded closed
second time was a loose negative cable at the batt