Mark,
When we did some more work on the heads and swapped the cam back in November, we removed a couple of the rivets when going back together, but didn't use copper spray or other sealer. The gaskets that were on the car at the time still had the rivets (crushed) and were not leaking.
I'm sure your car will be very quick...as I recall it was already running 109 mph with the old motor. It's a very nice looking car too, I saw it in Elkhart last year. I love how you put the SC rear bumper on a Cougar.
David