10w-30, 25psi at temp at idle
To me, the "at temp" pressure looks good, as does the oil viscosity used. I'll concur that a stock oil pump spring might be a good option.
Used to be that 10psi/1000rpm was the best criteria for doing an oiling system. With better oils and related basestocks (even for non-synthetics), this rule has tended to soften a bit. In addition to the real need for heavier oils for perceived better protection.
For years, I ran Castrol GTX 20W-50 in my '70 Monaco 383 "N", with good results. With other oils, it would start to bang-out just before the shift points. Going to that oil stopped that. At the time, many called it "motorcycle oil". I figured if it was good enough for Autobahn burners, with their smaller engines running at higher rpms, with their generally narrower bearing widths, it ought to be great in a big American V-8 (with wider bearings) at our normal highway speeds. Used it in my '77 Camaro 305 from its first oil change. But when the 305 was swapped for a 355, it started that engine's life on Valvoline 30, then went to 20W-50. I could tell a difference in response and power, just a very small amount, but enough it didn't feel right. So I changed to 10W-40 and everything came back. Heavier oils take more power to drive the oil pump, affecting power and economy . . . enough that OEMs seldom use anything heavier than 5W-30 now in cars w/gasoline engines. I did end up with Rotella T6 5W-40 syn later on, for the zddp levels (which are still above the old "SL" level, usually greater than 1200ppm).
When we built the 355, I spec'd a high volume pump, but with a standard spring. Just wanted something better than stock. End result is that with modern oils, much of what we knew "as good" in the '60s needs some updating in modern times.
Just some thoughts,
CBODY67