I run 34 on the street 360 and it is fine. They are all going to be different. Mine has a Crower 267/271 cam in it with stock pistons and headers. Try it at 33 and see what happens.
Is your distributor recurved so that the mechanical advance is fully advanced at the desired RPM. If not if your are measureing 35 degrees at say 25 hundred you will have too much initial becaue the advance is not fully extended and still advancing at a much higher RPM.