If your Taco pump is like the one I worked on with 2 smaller holes next to each other rather than 1 in the middle, then you can't drill it out. The restrictor on the one I worked on had a large air gap in the middle so drilling into it just opened up the whole area. Kinda sucked..........but now I know. 
I completely drilled mine out to 5/16" then filled it with JB weld and then re drilled it to 12/64 or 3/16" i might need to go up to 13/64 because...
Well its all done and back together AGAIN! and the darn thang dont work right. If im sittin still in the shop tires on the ground it works great feels good and super easy to turn the tires. If i turn the wheel too fast or at a normal turning speed its like the power steering has gone completely out!!
I guess i should check out those saginaw pumps. cause I know everything is correct I have pulled it all apart 3 times now! This is givin me such a headache. It wont even turn as easy as a regular stock steering system.
Any one got some more input?
And i replaced my nicked teflon seal with a good one!
