Thanks guys - great discussion.
For now I am going to mount the solenoid valve near the oil filter area. I have a Canton control valve which is a little pricey, but has a mounting pattern in the end, and a port for the pressure sensor in the valve body. Don't need a tee for the pressure switch. Less fittings, lees places to leak.
It will give me time to find a place the the Accusump, and then just need to run the line to the valve inlet.
Plum Bad. I will look at the firewall when the engine is back in the car as a possibility.
Thanks again - John