Simon, I am definitely doing a water pump cover and crossover tube delete similar to yours though, I hate the fact that my headers are so close to the crossover tube and oil cooler. what did you use for machined parts in your oil cooler delete to block the oil and water passages?
Well I had the front cover off at the time of rebuild and welded it closed
Last year I had the water pump just sealed off ( bulky )
I just made a plate that hooks to the rear adapter plate to attach my new coolant line
The oil is easy and I think Ppe still sells the plate that enables us to run hose off the in/out of the oil gallery
It's pretty straight forward
As for the check valve I'm just referring to that as the same reason some people would use one on oil lines for turbos so it doesn't drain back for start up, you would likely want this as you would loose a lot more volume thru larger lines and a cooler