[Cool Hand Lurker]

Years ago I read an article in a car magazine about a shop that cleaned flathead V8 blocks by baking them in an old oven at 300º for several hours. That cleaned off all the dirt and grease and flipping them over and over on a piece of plywood shook loose the rust and scale.
Find an old electric kitchen oven that has the self-cleaning feature which heats everything up to 500º for a couple of hours and burns off all the spilt milk.
But be aware that plastics all melt at about 400º so you want to take everything possible off the block first.