Is this a good deal for a 340?

.040 over is the max you can go on a 340. Also means that it will be the last rebuild on that block unless you resleeve the cylinders Big $$$. I picked up a std bore 340 for $800 and then spent $2500 on the machine work. It needed to be bored .020 over but I know that I have at least 1 more rebuild out of that block if I need to. $600 is a good deal if the machine work has been done and done right. I would check on who did the work and then go from there.