$50 For a ground cable....
thats just wrong.
I would make one up first.
I wouldn't just toss parts at it till something worked.
Clean all the connection, use your tester and check for continuity between the ground post on the battery, and the cable end, then do the same from post to the engine, and again from the post to the body.

Now repeat with someone turning the key to start.

You also really need to watch the battery voltage when you turn the key to start. Is the battery staying high in the voltage or is it dropping voltage under the load, ie the battery is bad or bad connection.

 

I figured it out today.

It was a fusable link off the negative cable. The big cable to the frame and motor was fine but there are two little wires that go into a fusable link about six inches from the battery and that melted its self together and disrupted the circuit. I cut the link out and put a bit of wire in and the truck started like a brand new truck. I got two 30 amp fuse links and Im gona plug those in tomorow in place of the fusable link.

 

i know the answer, its circled on the grill FORD

 

Just remember that FORD designed the front end under your XJ.....

 

I dont care lol gotta get my digsnin on ford when i can man

 

simmer down now you two. lets not get all over some junk pos ford.

 

Im simmered i was just flippin sum crap i like all types.of rides old cars.i prefer chevys. 4x4s im.a jeep guy i did.have a lifted ranger i do miss.that