40 psi oil pressure when the oil is hot and the car's at idle sounds high to me. You may have an issue but I don't think you should be shooting for 40 psi at idle. A rule of thumb is 10 psi per 1K rpm.

 

I just rebuilt mine with an LT4 kit and recon-ed everything, brand new block etc. and the 40-50 psi hot idle is normal for me, cold its at about 60-70ish, cruising hot its about 50-60, its not worrying me at all since its not going over 80psi and blowing lines. I plastigauged everything to make sure all my oil clearances were right in the middle of the specs and im using just a standard melling M55 pump with a hardened shaft. IMO its much better than 10 psi hot idle, or 2 psi idle when i spun my cam bearing which is why i had to do a rebuild. First get a mechanical gauge on there, use the port on the back of the top of the block right where the electric sender is. Another possibility is maybe your oil pump pickup fell off? I tack welded mine in place to solve this issue.

 

Mine was welded on when it was installed.