Re: 1974 MGB distributor drive dog- which one is i
Does Pertronix actually sell the 45D4 with no dog on it?
If it's an honest-to-God Lucas part that they've rebuilt the shaft will be pre-drilled for the dowel pin that secures the dog to the dizzy shaft. If the new dizzy comes with no dog, press the pin out of your old dizzy so you can remove its dog. Move the old dog along with any shim washers between it an the dizzy housing, and press the pin back in to secure it.
Any place you could install a 25D4 you can install a 45D4. The top half is different due to changes in the advance weight system, the part that goes in the block is the same size. If you wanted... you could even put an old DM2 dizzy in the MGB block. They didn't change for decades. The 45D4 will fit right in your MGB block.