Thanks everyone for the love. I appreciate the suggestions. Everyone will take their own path in a situation like this. While I haven't thought everything thru, and there may be some ideas I haven't thought of, here are my thoughts on the suggestions so far.
Used engine
There's no way to know how a used engine has been treated. Does it have a bunch of over-revs? How often was the oil changed? What are the odds a replacement engine has bore scoring immediately down the road? There are so many potential issues that could crop up and you don't know the condition of the engine you're putting in. My 08 CSS uses a 3.4L M97. You might be able to find some cheap 3.2 M96s, but that's not going to be plug and play in my car. I just did a quick check on ebay and the cheapest used M97 was $7K. When you throw in shipping and installation, I could do 2 used engines for the price of the rebuild. But how long would the replacements last? I could be doing the 2 swaps in a yr since you're buying an unknown. There are people advertising rebuilt engines for $12-13K but you need to know what's in them. One of the popular rebuilders in that price range doesn't use aluminum cyl liners. I see one on ebay in that price range from Germany but not sure what's in it. There isn't a ready source of available engines in my neck of the woods, so anything I buy will require a fair amt of shipping costs. I'm just not excited about doing this multiple times.
Keep driving it
We don't have a state inspection in Neb, so I could pull the cats and keep it full of oil but the potential crack in the cyl wall spooks me. If a chunk falls off and rattles around in the crankcase, it could cause nasty damage. I need this engine to be rebuildable or a good core.
DIY build
My dad was an excellent mechanic but we mostly did body work. Of course there were the normal maintenance jobs that he taught me how to do, but we never rebuilt any engines. I don't think this would be a good jumping off point to start. Plus I'd probably need to buy a bunch of tools. If it was a Ford flathead, I might be willing to try but these engines are a bit more complicated. I watched the Boosted Brothers videos of them buying a bag of Porsche engine parts and struggling to build an M96 engine. They're way more experienced than me. And my 2 car garage is probably not ideally set up for this either. As Clint Eastwood says, "A man's gotta know his own limitations".
LS swap
My brother suggested this too. If I had a garden variety CS with a ton of miles on it, an LS swap might be a consideration. But she's one of 700 Sport models, of which only 100 or so were brought to the US. You could get the Sport in 6 colors, so not all of them were Signal Green. Not that she's going to be a 6 figure car someday, but she is special and LS swapping would feel like I'm desecrating her. Plus I was raised in a Ford family so my dad would be spinning in his grave if I put a Chevy in any car I owned.
And I guess I didn't mention this is my original thread. There really isn't anything out there that I like better. That red 14 CS I had as a WD car 1.5 yrs ago was about as close to tugging on me as anything, but there were several things about it I didn't like vs my CSS. Anything I would buy would be expensive due to COVID. A 14 CS is now worth $48K. I would probably only get $15 or maybe $20 for my CSS in it's current condition, so I'd have to spend $25-30K to get into a 14 CS after selling my CSS.
Another suggestion from my brother was to sell my LE to pay for the engine rebuild.
Yeah, right. I know Frodo just got excited reading the first sentence of this paragraph, but it aint happenin. I love both of my cars and don't have any desire to get rid of either of them. Before I got them, I changed cars about every 4 yrs.
I should also mention my house has been paid off for almost 13 yrs and both my cars have been mine for 11 and 7 yrs.