That's a VERY Good thought about the supporting hardware! It could be the difference between a dog and a new tires each week. I am still fired up about the cubic inches in a decent weight block. Quote Tim Allen here - "AR AR AR AR!"He asked about a particular 408. Displacement doesn't dictate streetability without all the supporting parts as context.
The specs on their site make that look like a truck engine. I mean...a 5100rpm redline. It would be a great street engine as-is, but you could probably benefit from more cam, especially if it's going in a relatively light Mustang.
To answer the other question, I have no experience with ATK. Their description of the heads is a bit dubious. The Summit product page doesn't mention brand, which means Chinese no-name to me, but ATK's site says they're Edelbrocks, and their catalog just says "aluminum."