Since I decided to convert from a cam driven distributor to a block mounted distributor, I would have access to the oil gallery plug at the back of the head.

I decided to access this point because...

...the oil pressure switch mounted on the block no longer uses 1/8 pipe thread, making adapting in an oil pressure gauge there a PITA; [and it is a bit crowded down there anyway]

...because the dash is not equipped with an oil pressure gauge;

...and I do want to monitor the oil pressure during initial start-up and during the break-in period;

...using this access point would allow me to hook up a mechanical oil pressure gauge easily.

With a pressure gauge tapped in, I can verify system prime and pressure before cranking; ie I can verify no oil leaks in the pressure system plumbing [turbo oiling, oil cooler] without having to crank the engine.

After the break-in period, I can disconnect the oil gauge; and the access will be there if the customer wants to add in an oil pressure gauge in the future.

An added benefit of tapping in here: this access point will tell me the lowest pressure in the system.