I believe the original question had to do with racing at your local Saturday night track.
With that said, there are some Saturday night tracks that are not very competitive and others that are very competitive. Also depends a LOT on how much grip is available in the track surface. Most Saturday night tracks, the track prep isn't stellar and car counts are relatively low, so the track never gets real "good," ie bites up hard.
I wouldn't hesitate a second to take one of our 2005 AO3 chassis to a local Saturday night track and be competitive for the win against ANY year kart. Likewise, you could take an '05 Phenom or '13 Triton and win with it locally. Seen it done regularly. Now, will those chassis be as competitive on a higher bite track with competition on later chassis? Likely not.
The evolution of kart design to accommodate higher bite (tracks and tires) has lead to running ultra-high cross and a different approach to how the weight transfers. For example, you could never plug 70%+ in an older chassis and expect it to work anywhere near what the newer chassis do.
Actually, PRC did remake some older chassis (specifically for syrup racing.) That's a whole other genre, but consider how many years the Phenom was the dominant kart on syrup tracks?
It's not about the year as much as it is matching the chassis design, spindles, tires, driving style, set-up, etc. to the track.
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