Is the 4 speed transmission from a 1947 GMC 3/4 ton Advanced Design the same dimensions as the 1948 on up? It appears the one I have is about 2 inches shorter and it does not bolt up to the bell housing on my 1950 Chevy 1/2 ton. I've heard that the SM420 (I think that is the correct designation for the later version 4 speed) did not come out until 1948. As they look so much alike, I always just assumed they were the same.