Great car! The most powerful Cadillac spanning about a century from 1902 until maybe when the Escalade (with 403hp) or maybe the V series.Had this short happen to me on a 1972 Eldorado where gas gauge did not work - same issue. My car was highly molested and had to order a used wiring harness to fix it. The problem was that the wires down by the starter had frayed/cracked insulation. Rewrap all the wires at starter with electrical tape and see if that does not fix it. Then you if that fixes it you can make it more durable/more appealing. I tried the kick down and all of that and it was down by starter. Hope this saves you some time.Put replacing the timing chain on your list. Check the CV boots for cracks/ruptures. Half the fun is getting them straightened out.
I have a 68 Eldorado that I put 300,000 miles on and I had a 70 Eldorado beater. I have not had any problems with the starters except normal wear and tear. Well, there was the worn timing chain on the 70 that caused kick back on the starter and damaging the clutch. Moral of the story…Change the timing chain. Sooner than later.