I am not 100% sure but I think I went to a full 1/2" on the Pump to the Oil Filter Adapter as did the guys at FECA FE Club of America. Pay attention to where that drill is going though. Speaking of Oil adapter I got a 428CJ that was prepped by Duffy's many years ago. The half hour or so someone spent prepping the adapter passages was awsome and certainly indicated the degree of the craftsmanship they used on the entire motor.
I never trust a Shop Washer since the do not get into the holes and they lack filters so that a pile of "dust size crap" can collect here and there. I would also suggest a real 2,000++ PSI blast with a pressure washer into the water jackets, passages etc followed by a spray everywhere inside and out of Phosphoric Acid/Distilled Water* to clean up those rusty areas, prep the metal surfaces for both paint and add rust protection and then prior to drying a rinse with tap water prior to final dry and oil. Its best to do this on a Sunny Hot Day and or have a heat gun to speed up drying.
*Always use DI or Distilled Water to mix with Phosphoric Acid as there is no calcium to weaken the acid. I prefer Grocery Store bottled Club Soda to add more zing and make it more peppy.
