That sludge isn't terribly bad- - - -you can still see the rocker arms! I'd suggest pulling the oil pan drain plug and using a pump-type garden sprayer filled with Diesel fuel to hose the top end down. I also use a mixture of engine oil and Diesel to run the engine, about 1/3 Diesel and 2/3 oil, to flush out the bottom end like a washing machine. Overfill the crankcase to the point the crankshaft and connecting rods dip into and splash the solvent/oil mix around. Run the engine at fast idle for 15-20 minutes and the splash will clean the bottom end in places you'd never be able to reach with a brush.

DO NOT DRIVE THE VEHICLE WITH THE SOLVENT ONBOARD- - - -NO LOAD RUNNING ONLY!

Be aware that an old, clean engine will probably become a leaky engine. Be prepared to replace gaskets and seals after the cleanup. Using gasoline for cleaning solvent turns the engine into a bomb- - - -don't do it!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!