Do you know that for a fact? The author of this thread gave no info as to what class he was referring to, so it is difficult at best to respond accurately. Back in the 70s I got deeply involved in what was 'legal/not legal' in NHRA S/SS. Even independent 'authorities' needed calling out for occasionally printed errors. One had to keep abreast of any/all casting/part #s and what 'massaging' was permissible, for ANY component. Maybe the rules have changed since then. :shrugEither Iron LT-1 Head is legal in IHRA or NHRA.