Thought I'd post this info. Planned to run the Keystones on my 73 340 Sport because I like them and had them on the new one I bought back in 1973. I know they're heavy. Talked to the folks at Cragar and told them I needed 15x8 with 4 3/4 backspace. They no longer offer a custom backspace. Said they might "sometime" in the future. Guess now I'll have to find a different wheel.