John, It's my understanding that putting the restrictors in the heads will neither increase nor decrease
oil pressure. In my case, I am looking at putting them in because I put in a high volume
oil pump and as a consequence I am pumping too much
oil into the rocker shaft/valve covers. I also understand I can put them in with the heads on the engine. I will just have to remove the rocker shaft. There are four bolts holding each shaft in place. If my memory serves me correctly, the second bolt hole from the left, as you stand facing each head is the one that has the oil passage feeding into the rocker shaft. I will be placing one on each side.
Rick