I'm with Ronnie - given the pump design that you have, it is severely flow constricted to begin with - so it doesn't make a whole lot of sense to just "open up the downstream".
If you're going to be running this engine at higher RPMs (real performance application), you might consider a few "mods" to the pump casting to make it like the USA 49-53 pumps. Now, that is assuming the REST of the pump is like ours --- most importantly the pressure relief system (which I can't comment about in your case).
Or, use a Ford 49-53 pump.
Here is the outlet portion of the 49-53 casting:
IMG_8780.jpg