It actually depends when in 1948 you are referring to, because in May 1948 the last two of the six Leyland Lion LT2 single deck buses were withdrawn from service. These had entered service in June 1930.
In June 1948 four new Leyland Tiger PS1 single deck buses entered service, these were numbered 97-100.
The four Tigers were all withdrawn in April 1964, to be replaced with four Leyland Leopard L1 buses, numbered 91-94.
The Leopards remained in service in 1969 when the MPTE took over bus services in Birkenhead, they were finally withdrawn in November 1975.
I lived in Trafalgar, L. Bebington, in the '40s-'60s and well remember these buses. The low bridge in question is on Bromborough Road just beyond the Quarry Road East junction going towards Spital Dam. It was the 44 route, New Ferry to Eastham Ferry, and I think it was the only route using these buses. Bri