The flip side of that there's really no way of knowing (or proving) actual miles.
I've bought a few Japanese takeout engines with good results - My SR20VE came from Soken (
http://www.sknengines.com/). No issues, good deals.
You'll need to budget for all new ancillary pieces, or transfer yours over from your current engine). Belts, hoses, alternator, starter, etc.