There are a lot of rarely driven cars with old cracked, hard 13" and 14" tires because they just don't wear the tread off them. A near full-tread 12 year old tire with 30k on it is a scary thing, I've seen 'em, on older Porsche's, MG's, Z-cars, etc.
If this is going on your Lotus 7 clone, and you realistically are only going to put a few thousand kilometers a year on it, then I'd say get something like the Toyo Proxes RA-1's, or Yoko A032R,, leave them full tread and enjoy. You may have to buy new ones in two or three years if the car is a rarely driven sunny-weekend toy, but it will also be the single biggest performance enhancer you can put on it, plus, it's a Lotus 7

, It'll be fun.
I've used them on the street/track on my street/track 911 and they can make a good dual use tire. I figured I got 5-8k out of them, depending upon how many autocrosses/laps were included. YMMV
Other than that, it's the Sumitomo Morty mentioned or hockey pucks.