When desiging something like this, the pressure is important, but the flow is more important. You can do a 5 gallon bucket test to see what flow you have available from that spigot, which is usually a 2 person operation. Take a 5 gallon bucket and a stop watch. Turn the water on to full flow. Have someone start the stop watch when you move the bucket under the flow. Stop it when the bucket is full. With that time you can figure out your flow available. Take your total time to fill the bucket and divide it by the size of the bucket. That gives you the flow time for 1 gallon. Take 60 and divide it by the time for one gallon and that will give you your gallons per minute.
WIth the gallons per minute, look at a flow chart for the sprinkler heads.
http://www.rainbird.com/documents/turf/chart_VAN.pdf
The chart shows a max reading for 30 psi, which you are certainly over. Something to consider is using PRS (Pressure regulating stem) heads which limit the flow to 30 psi, reguardless of the input pressure. This will allow you to know the exact flow needed for that zone.
If you would like to post the layout (Van 8's on 90's, 180's, 270's, and 360's) and the time to fill a 5 gallon bucket, I will be more than happy to assist you in setting things up.