CAUSES? High oil pressure

Hey guys my 1968 barracuda with a 440 Magnum just jumped from marking half way on my oil pressure gauge to HIGH- I did he oil change and new oil filter I used 20 -50 high mileage oil

What could be going wrong here
Oil too thick?
Bad oil filter?

HELP- thank you :cheers::cheers::blackeye::angry5::lurk:
:lurk::coffee2: