The fins on the bottom will need grinding down to clear the early-LS1 coolant pipe setup (vents to all 4 corners of the heads). Or you can replace with the later setup that only vents the front corners, but hard to buy them locally. Seems to be worth 5-10 rwkw depending on other mods, stockish motor will be at the lower end. Worthwhile if you can pick one up cheap (seen em go for $50ish on ebay).