Ok, just went out and re-checked it (with a light this time) and there is a slot in the rod, but I looks like the slot is only on the top of the rod?? I guess the tab on the old one broke off when i was removing it.
Used a mirror and there is no slot on the end of the rod, and none that I could see on the opposite side of where I'm seeing a slot. Seems to me that slot would have to be all the way through and all the way out the end to slide it in there. But it does have a slot. Sort of. I sprayed some PB Blaster on it in case it's just crudded up, but I also used my box knife edge on the end of the rod to see if I could scrape anything out of the way to expose a slot, but no luck. I'll go back out and wire brush it a bit. I may have to end up cutting a slot, but at least now I know there was one there, and my old spring is probably not in it's original condition. I'll report back.