3837004 is a 55-57 235.
Melling makes new pumps for our old inlines, and they can be bought from any good parts house, but you may find it cheaper through Patricks...
As for mounting, to remove the pump, you just remove the setscrew and unscrew the oil tube and give it a pull. If that won't do it, use a hammer and punch through where the dizzy goes. The part that the setscrew is mounted to, and is held onto the block by headless bolts THAT YOU AREN'T SUPPOSED TO REMOVE, isn't part of the oil pump. It isn't supposed to be removed because it is machined WITH the block, not separately. By removing it, you run the risk of screwing up the alignment between the oil pump and dizzy, with the possiblity of breaking the dizzy shaft, or trashing the gears.
