This is a two-part answer.
If your car has stock fenders, I would stick with standard 165R15 tires because anything much wider will rub.
You can get fiberglass fenders for Bugs that will let you put any width tire you want on there.
VEHICLE: 1968 VOLKSWAGEN BeetleStandard 560-15 155R15 Radial Recommendation: 165R15
165R15.
I don't think doughnut spares had been invented then. In any case, the 1968 VW Beetle, as with all Type 1 Beetles, has a full-size spare.
Original Equipment Size:
P165/80R15 is the standard size.
165/r15
165R15 is stock.
165R15
165 r 15
18'
165/-15
165R15 86T