Only real way to remove the 60 years of petrified dinosaur dung is to remove the head, all freeze plugs, and water pump and manually dig at the crud from many angles. Once the big chunks are removed, a steam jenny works great for the rest of the job.
It is my opinion that if you do anything less than this, you are:
a)kidding yourself, and
b)if you don't take it apart, you are not going to know how badly clogged your water jacket actually is.
Carl
