Yeah, concrete so it will sink even faster and make a better anchor.
(Sorry, just wanted to be the first to get to pick on an Oldsmobile for a change).
I know the last set of head bolts I picked up for my BBC came pre-coated with a teflon on the threads but I don't know if the same would apply to the Olds, that is, I don't know if there are bolts that run through into water jackets.