If your buying the budget ford crate motor, it will be a roller, so it will be a block from about 1990 to 1997. If you are getting one of the higher end motors >$10k, it will be a NEW Boss block. Ive talked to several very trusted machine shops and they wouldn't own anything with a Boss block. They are ok and all, but the metal is full of porosity and generally not worth the price they gouge you for it. If you want a quality aftermarket block, you cant go wrong with a Dart block or a BBE block.
If your budget is slim like 99% of everyone, make sure you do your homework on the engine builder. Make sure you know what parts are new and what parts are used. You can always tell them, hey your motor is fine but I want a new 4340 crank and 4340 rods and SRP pistons balanced and blueprinted. Combine that with some quality name brand aluminum heads and you will be very happy. Don't expect a stock build to be anything special at all. I got a stock 302 in my truck and I could barely tell any difference between it and the 300k mile worn out engine that came out of it, other than it ran much better and got twice the gas mileage and didn't leak a quart of oil per week.
