For what it's worth, when I had my radiator recored with a 3 row recently. The guy gave it back to me with a 4lb cap. Said that was all these ever needed. When I flushed my block a few days ago, I already had the head and water pump removed. When I applied water thru the rear holes in the top of the block, behind cyl #6, that was where the greatest amount of rust and sludge came running out. And I mean incredible amounts. I'm still trying to get the rust off the driveway. Flushing thru the front of the block from the pump opening DID NOT remove any of that junk. I am still considering pulling the freeze plugs as Wrenchbender suggested, and doing another flush, even though I did not have overheat issues with the half clogged one row that was in there. I know it's alot of work, but my vote would be to pull the head, and flush it right.
