The straight pipe "A" is for an engine with the front motor mount. The pipe with the angle "B" is for the engines with the side motor mounts. You might also notice that the "B" engine has the fuel pump with the offset inlet and outlet lines. The vacuum advances were also different. All to accommodate the side mounts used in automobiles.

I have a 1953 235 powerglide engine and it looks like the "B" engine.

Kurt