[RICK LAKE]

Undy Dave the only thing I would do is to have only distilled water and water wetter in the coolant system. This will not destroy the bearings like coolant. That milk shake in the motor is DEATH.
Is it possible you can get a coolant dye to add to the coolant. Run the motor and drain the motor, You need to drain the motor through the bottom of the block and raditor. This should leave you with just dye stains where the coolant is leaking. If you can get the ports or area clean and dry enough, My thought would be to try Tig welding it first, if this doesnot work, GREY RTV sealer, coolant and cover the ports where it is leaking. The other would be to use a plastic paint that expands and retracts.
GM still sells the tablets for aluminum motors we used for all the older Caddies in the 80's and they do work. The area you are working on is a low pressure area. If you can get 30psi to hold in a hot or cold temp you have it beat. I would only use 100 psi on heads and blocks after being sonic checked.
I think it sucks that you spend alot of money on parts, have port work done, have the parts installed on the motor and after 10 to 15 heat cycles that damn problems start with questionable parts. Has anyone had problems with EDELbrock heads leaking with some head work, Joe? George? Keith? Barry? Brent? See what I mean. Rick L.