If my gauge is working correctly, mine is also around 35-40 Idling and up to 75-80 while driving. Was going to try and track down the builder that rebuilt it for the previous owner and see if it has a 80 PSI pump possibly or if I should be concerned?
You could get a pressure gauge and put it in the filter adapter to check if your in dash gauge is correct. I've found the pressure gauges to be off by as much as 10psi.
The standard oil pump pressure relief is 60 psi, the high pressure pump is 80 psi. One has a stronger spring, once the pressure builds to the strength of the spring it opens and lets some of the oil into the intake side of the pump controlling pressure. That makes no difference at idle as both springs will have the relief closed. High flow pumps have a taller gear for more volume.
Pressure is a result of flow and resistance to flow. At idle the pump is not turning as fast as it is at 3000rpm, there is less flow at idle than at 3000. If there is no restriction to the flow of oil the pressure will be low, if there is a restriction to the flow the pressure rises. Tight bearing clearances, say 0.001", will restrict the flow of oil more than a greater bearing clearance, say 0.0035", so with the same pump and rpm the tighter bearing clearance will result in higher running oil pressure than the looser clearance. If you have a fairly constant oil pressure an suddenly it starts to run low, it's a good indication you have a bearing going. Along the same line, if you have a fairly constant oil pressure and you notice the pressure getting higher it could be due to debris in the oil filter restricting the flow of oil.
Debris in the oil filter will restrict the flow of oil through the filter, the more debris the more restriction, until the filter adapter bypass opens and allows unfiltered oil into the galleries. Not good.
If you are worried about it you could always take the filter off, cut it open (don't use a hack saw) and spread out the paper filter element to check for debris. If it's clean you know it's not the filter causing the high pressure.
When I rebuilt my engine the machinist tried to talk me into three and a half thou clearances. Said all the "race engines" have greater clearances. I said I'm not building a race engine and don't want to see an oil pressure needle at the bottom of the gauge while sitting at a red light in 100 degree weather. I told him I wanted two max. When I inspected and measured after I got the block back I had 3.5 thou clearance. I had to take it back and get him to redo the mains.
Forgot, just because one has a high psi pump does not mean there will be a higher oil pressure when running. It's just the point when the relief valve will open. If the engine is built with extra large clearances it will run with lower pressure no mater what the pump relief valve rating is. If all the clearances are tighter the oil pressure will be higher. More restriction-higher pressure, less restriction-lower pressure. I knew a guy who was running a Triumph that had low oil pressure, he put a shim under the relief valve spring and was surprised that the oil pressure didn't rise. All the bearings were shot he could have closed the relief valve with a plug and the oil pressure was not gong to get any higher.