Unless you want to compete with the car, I would not recommend 55 profile tyres on a trad Morgan.
Agreed that most modern rubber is going to lower profiles and so some of the best buys are found there , but the smaller side wall will hurt the ride quality and not help the handling.
A lot of Morgan owners go the opposite way and fit higher profile tyres (Like Griffo above) this improves the ride quality and will have only a minor effect on handling.
If you experiment with tyres sizes it is bets to use one of the tyre size calculators in order to asses the effect on speedo readings etc , there are ways to reprogramme the speedo if the difference becomes significant.
