It shows in this video.   http://www.youtube.com/watch?v=Q7ZjObWyRJU

It shows in the video.  The old way to do it was just to pinch the overflow tubes all I've done is tap one tower for a 5/16" x 1/2" bolt and shoulder it to locate the rocker shaft.  It's also a good idea to slot the oil holes on the shaft to better oil each rocker.  There has been some concern about oiling the timing chain when the overflow tube to the front has been deleted in this case I drill a small hole in the front of the block to feed a little oil to the chain.  There are some on this site that still run the over flow tube with no problems and of course that is the way Ford intended it but with these few modifications I still like to pressurize the ones I build.

This slot is cut into the tower that will be threaded for the locating bolt so air will be bled out of the shaft.

I use one of those lead hammers with the plastic screw on faces that are green and red. as far as pressurizing the rockers, there is a passage in the head between the head and block that makes a couple 90* turns. when the rockers are pressurized it will slow the oil flow through this area and being the hottest part of the path of oil flow the oil could start to bake the oil there and block this passage. this area was the culpret of much of the engines loosing oil flow to the rockers. So I am not the biggest fan of slowing the oil flow through this area. I understand oil may be better these days and withstand more heat, but the slower it goes through there the hotter it can get. I am more to letting the oil flow through there fast and freely to keep it clean and not have the propensity to heat up and plug up like cholesterol plugging up an artery.

6 in one half a dozen in the other, just more food for thought.

I am not saying pressurization is not good, it is good because it forces the parts to float on a film of oil preventing wear. I am just looking at things from all angles and think too much restriction may lead to what I mentioned in previous reply.

This is sort of like talking about oil brands.  You’ll find arguments for and against pressurizing the shafts.  Here’s a previous thread on the subject.  Be sure to read all pages and then come to your own conclusions.

Pressurized rocker shafts

its like the old argument about viscosities also, some say thicker is better some say thinner, the thicker because it gives a better cushion and the thinner because it flows through quicker and stays cooler. I tend to be on the thicker side since my engines sit for months during winter and when I travel jobs. In my opinion the thicker will hang in the bearings longer and not drip out so that initial start after sitting a couple months has a bit of cushion. I think thinner the bearings drip dry and it is that initial start where 90% of wear comes from after sitting.