Personally, trying to save cash at most turns, I prefer the hands on approach. Especially seeing you have it on an engine stand allready. I would scratch and chip away at it for a long time removing all the large chunks, then I will wet it all down with a good quality degreaser and scrub away with a good stiff brush, then usually a garden hose with a fairly strong nozzle will remove the rest. This has worked on many an occasion for me to get an engine really clean. You will also find that afterwards the plug you used to block the dizzy port isn't "in" the block backed up with a load of water and some of that 20 year old crap you mentioned. Sometimes the slow cheap way is the best IMHO. Good luck