I have had great luck with JDM engines (other Toyotas, not 5vz's), but the quality is HIGHLY variable. As is the '<50k miles' claim. You can definitely get good ones, but also bad ones.

Here's the top end of a 3S-GE BEAMS engine I got when it was ~20 years old:


The 3S-GTE in my current Camry was similar. So, find a good one and it will likely be the best bet. Find a bad one and you are *not* going to have a good time...

Also, to be clear... the 5VZ's from a JDM vehicle are built in the same factory as the 4Runner engines were. Same quality. There are some (possible) quality differences between Japan built and US built 2UZ's though - so it isn't always apples-to-apples.

-Charlie