I have bushed lifter bores in my block so a restriction to the pushrod side is somewhat there. As far as the need to restrict the stock type system, tread lightly here. You need to make sure the shafts get plenty of oil. If i were to run pushrod oiling on a shaft system i would use restricted pushrods. Depending on what is available i would try .030 in each pushrod for starters which from my experiance would likely be enough. I could only get .040 from Manton and i have plenty of oil up there. Keep in mind extra oil takes heat away from the valve springs which is needed. The springs. I use for .870 and .800 lift are holding up very well at 7400 rpm and a lot of that has to be the large amount of oil going up there.
