Easy to check the condition when it’s in that stage.
Go for it if you need it and the price is right.g

Looks like more than 200 miles to me on that piston.
I have never taken a 200 mile car engine apart but I have a lot of two stroke bike engines and they looked better than that.
That picture shows the piston top has been aggressively wire brushed as well.

Just my thoughts, but I would not spend penny one on stock internal parts for an engine when I cold just buy a running 5.0 for $500 or less.  Its a significantly better place to start with as a fun engine due to the factory roller cam, slightly longer stroke, etc. 

Also if the owner is building a 347 out of a 289 he's not too sharp, or got bad advice.  The cylinder skirts don't go down as far in a 289 as they do in a 5.0, leading to the pistons coming too far out of the bores at BDC.  It exacerbates the wear in an already wear prone stroker package.  For performance use most shops will advise you away from a 289 block for building a stroker.