Whereas TCs were rather spindly looking, the TDs seemed more substantial. They too eventually needed modernization, so the TF, which I wrote about here, was introduced. There was a limit to how many model years prewar styling would be viable in the American market, even for a sports car. So for 1955 the redesigned MGA was introduced. I posted about it here. The A received a new frame along with the new body, but its wheelbase was the same as the T-series MG just mentioned -- 94 inches (2,388 mm).
The MGA proved to be a short-lived transitional model. It was replaced by the MGB, a considerably modernized design using a unit-body instead of body-and-frame construction. Its wheelbase was slightly shorter at 91 inches (2,312 mm). Its length was 153 inches (3,886 mm), again shorter than the MGA at 156 inches (3,962 mm), whereas the older TF was 147 inches (3,734 mm) long.
The MGB was long-lived, versions remaining in production as late as 1980. However, it was long out of date stylistically and engineering-wise by that time.
The images below feature an early B from 1963 that was advertised for sale. A few photos of previous MGs are included for context.