Well I guess that IS the main concern about 40 year old rods, what do you know of their history? I stayed with my Le Mans rods because I had run them previously in my original motor and had turned it to 7000. In that respect I was pretty confident of their ability. I had them worked over, during my build, checked out, etc. My new rpm is around 6200-6400 max and so far so good!
I think I spent about $4,000 on parts/machine work for my build. The rotating balance was exactly $300, by the way, (Keith nailed it)!
There was no way I could have gone $15K at the time. Sometimes us 'po folk' just have to risk it...
I AM surprised a Le Mans rod, having been checked out, would fail at a measley 5000 rpm, clearly THAT rod was defective in some way.