I would be leery about using a high pressure pump. We used one on a 350 rebuild. During cam break-in, at 2000 rpm, we had about 80# of pressure!! It caused more problems than it was worth, in terms of leaks, etc, and I finally put the standard spring in.
I would say 15#-20# pounds at idle is ok. As stated above a lot depends on the quality of the gauge.