1973 Dart 318 core plug replacement questions

There were shallow cupped plugs and deep cupped plugs in the 1 5/8" size. I ordered one of each in brass.

The OEM original steel ones lasted 50 years. I'm going to attempt to replace just the leaking one for now with the engine in place. I was really caught by surprise that I might have to pull the engine to replace deteriorating core plugs when this leak popped up. I guess I have to plan on that in the future when the other ones start leaking. My last two leaks on this car are a core plug and a rear main seal. I already fixed a leaking water pump, leaking power steering box, and leaking transmission.