Yeah you can drill the oriface without assist but it won't really give you what assist does. Shimming the spring tends to give a little added push but it will wear out a pump real quick. I've heard many people that have shimmed the spring and after killing their pump, they won't do it again.
On other boxes, you just need to know where the 2 port veins run through the box. I'll be doing my new Saginaw box here in the next few days and figuring out where the veins are wasn't too difficult.