They are tyres for two wheelers. Yes the internal design is different... Can't help wondering whether tyres for sidecar (i.e. flatter tread rather than rounded) or Longstone / Blockley traditional style car tyres (those tall skinny ones as seen on vintage cars) may not be a better bet. Just an example, but I know Russ (former lead at Prescott Driver's School) raised the pressure on BHM's +4 Morgan by some 14 - 16 psi over the road pressure. He thought it handled reasonably after that (he's not a Morgan person ).
Cheers,
Graham (G4FUJ)
Sold L44FOR 4/4 Giallo Fly '11 MINI Countryman Cooper D All4 '90 LR 90 SW