Yep, same tires as old beetles.

Performance upgrades... I sense a long thread coming up here.

Suspension (in this order of priority):
Urethane and/or Delrin bushings throughout.
Bilstein or Koni shocks.
Stiffer springs, optionally lowering the car as well.
Larger front swaybar, optionally adding a rear swaybar.
Wider wheels and tires.

Power:
Evaluate what you have first. Worn carbs and distributors don't make much power. Neither do badly adjusted valves and generally poor tuning. Nor does the stock tiny exhaust system. That stuff is relatively cheap to fix, so simply fixing it is a lot of "bang for the buck."

Replacing a worn B18 with a sound used B20 is a good step up in torque. If you have a sound motor and you don't want to rebuild, about all you can do is go for a bigger cam and lose some low end power.

Well-built street performance motors start at around $3500, if you do most of your own work, and go up from there. You can pay more for a badly-built street performance motor as well. If you really want to pay a lot, you can double the stock power (or more) and still have a tractable car.

It's easy to convert to an overdrive transmission if you have the plain 4-speed, and well worth the trouble. If you have an automatic, the conversion's a lot harder.

If you have a '67 or later sedan, not a wagon, you can swap out the rear end for an 1800E/ES model without a lot of fuss, which gives you 4-wheel disc brakes. Not that the stock brakes are inadequate...