I've seen some anecdotal evidence that early first generation RX-7 tubs (1979-80) are a bit (50-100 lbs) lighter than the later models. Most of the ITA/7 cars that I've seen that are close to minimum weight (adjusting for differences in driver weight) seem to be based on early tubs. No obvious reason this should be true. Visually they look the same except for some bracing near the rear wheel arches that is found on the early cars.

So, has anyone ever actually weighed both and determined if there is actually a difference, and if so how much?

Thanks