I have purchased a few engines from Auto-Zone over the years, and they sem OK. They are reman'd by an outfit named "Recon". For the price they are OK, but nothing high-peformance...just a straight rebuild.
I paid $1,200 for a reman'd 403 I put in a Trans/Am and it had no problems. I put about 70,000 miles on it before I sold it and it was good to go. But is was certainly not a hipo engine.Just a station-wagon motor...like the original 403 that came in it.
But that was several years ago. With all the crate motor deals out there today, there are probably some much better bargains to be had if you look around a little.