Ground connections

I picked up my first Subaru last week, a 1990 Legacy L sedan. So me being a bit of a gear head and also a Subaru noob, I've been poking my head around under the hood getting a good feel for what is where.

My first inspections of the electricals have come up with some needed repairs. The knock sensor plug, the harness end of it is missing the outer sheath of the wire about 1-2 inches back from the plug and the wire that is between the inner core and the outer sheath is not going to the plug. Is there 1 wire or 2 that goes to the knock sensor? Shouldn't that throw a knock sensor code if the wire was broken? There's no CEL light on and I know it works it flashes at start up.

There's a ground wire, it think it's the transmission ground, in the middle by the fire wall that goes down to the tranny, mines a manual. On the tranny end the ring connector has been broke off and the rest of it was jammed under a clip like thing on the top of the trans casing. Where does the trans end bolt to?

Pics would be wonderful for the ground reference but I would appreciate any advice you have.

Thanks

Ok so I fixed the trans ground wire, still not sure if it was supposed to have one but it does now. If it doesn't have a ground where was the other end of that factory wire supposed to go to?

The knock sensor plug on the harness end is very chewed up after I took a closer look at it. Looks like someone used a screwdriver to get it out. I want to replace this wire and plug with another one.

What year range and model would I be able to get this from? I live near Flint, MI and there's not many Subaru's out this way, this is GM town, so the boneyard has slim pickings.

Would I have to splice it or does it have a plug on the other end?

How far back into the harness should I put the splice?

Thanks