Is this a good engine for the price

What are you planning for this car and engine? If wide open racing, then it MIGHT be a good candidate... which it sounds like if you have a narrowed rear axle . For street cruising, it is overkill.

There is NO mention of condition or how much it has been used; this engine may be totally run out. Is there any chance you can go see it and pull a head to make bore measurements?
Mostly just street but there are about a million assholes with mustangs around here and it would sure be nice to eat them alive