I have done this, sort of.
I didn't have to replace the engine, but I did replace every hose, and nearly every ancillary oil seal, and a slew of other stuff. What I paid for the car, plus what I paid for parts to fix pretty much every issue the car had (doing ~70% of the labor myself) equaled about the same as what a well documented ~100k mile '91/'92 car would cost outright.
If you're masochistic like that, or if you want to spread the ~$10k or so over a year or two of picking at various problems, then sure, you'll still end up with a really nice car that will be fun to drive. If you are looking at it as an investment, or if you would need to sell it without taking a big loss, then it would be better spend the money up front to get a well documented car.