David, The similarities are few and far between regarding the 1947 and 1948 Cadillacs. The bodies are completely new, with nothing being interchangeable, other than the chassis and engine. It wasn't until 1949, that the new OHV V8 was introduced. Even the dashboard is entirely different. It was quite a change that year for the Oldsmobile 98 also, which shared the body with Cadillac. Never the less, it was the first new GM body, after WWII.
Cadillac never made radical changes each year, but evolutionary changes, to keep it's identity. Being independents, Studebaker and Hudson were able to make a radical change after the war, since they had the money from war contracts, and didn't have to go through a big board of directors for each decision.
I find the 1948 Cadillac a rather attractive new car, definitely a post war design, with the trademark fins.