Sorry this happened to you. I think with e9x m3’s it comes down to the way the previous owner treated it vs mileage as a indicator for rod bearings.
When I bought my e92 m3, it was single owner and he told me about how he does the start up procedure, never revs past 3k until it’s warmed up. It was a 56k mile car when I bought it but the way it was treated with lots of care was more important.
You bought a 47k mile car but it was probably treated like shit it’s whole life, warm up never taken seriously, reving high when it’s cold, and just beat on.
Just LS swap it at that point. It’s challenging but you have the experience.
I saw somebody swap a LT4 into a e92