MG B Inner Tubes
An early MG B would fit a 155R14 Michelin X. But then the majority of MG B’s fitted a 165HR14 Pirelli Cinturato CA67. This Michelin inner tube is the best possible inner tube for either of these sizes and perfect for an MG B.
There is a possibility that your MG B may have been fitted with over sized tyres such as a 185/70R14, under these circumstances you will need a 14 E 13 Michelin inner tube. And the best tyre would be the 185/70VR14 Pirelli Cinturato CN36. However the best tyre is the original 165HR14 Cinturato CA67.
If you car has been fitted with some lower 65% profile tyres then you should not fit inner tubes. If your MGB does have wire wheels then you should always fit an inner tube.
Morris Minor Inner tubes
The Morris Minor originally fitted crossply tyres 5.20X14. However the best tyre to drive your Morris Minor 1000 or Traveller on our modern roads is the 145HR14 Pirelli Cinturato CA67. And the best inner tube for these cars is this Michelin 14 D 13. Other good tyre options are Michelin’s 155R14 X. however these lovely little cars handle better on a period 145R14 and the Cinturato is the only one.