I'll echo what Tony said. Most of the differences are weight related, plus a few improvements in design. Birdcages weigh probably 1/4 of what they weighed when I got my first sprint 33 years ago, I think about how they were back then and wonder why they were made that way. In the seventies they used in/out boxes, now they use shifter rears (basically the lower shaft is a coupler). Spun aluminum wheels now as opposed to magnesium in seventies. Aluminum radiator over brass, aluminum rear axles, titanium fasteners, 2 wheel brakes. My 1984 Buckley weighed (according to Jonathan Swanson who bought it), 1825 pounds, probably heavier when I had it, we didn't have a weight rule then. We were running against cars weighing 500 pounds less.