I don't have the plans but,, my tank at home is a "salvage drum" converted to hot tank with agitation. A salvage drum is a large 55+gallon drum that they put leaking regular drums into. It is heavier material and has a removable lid.
Mine was made by welding two hot water heater element bungs into the sides about 8" above the bottom. then screw in some universal heater elements, hook them up to a used hot water heater thermostat mounted about half way up and you have your heat source.
The drum has a bung down low on one side that I use to empty the fluids when needed (don't just dump the effluent, the EPA will get ya!)
In the bottom of this wonderful piece, I made a removable stand, About 11" from the bottom so the items inserted in the water bath wouldn't contact the heater elements. Mine is made of 1/4" strap about 2" wide (looks like a cherry pie lattice crust).
I then plumbed an old high pressure pump (carbonator pump from an old soft drink unit, I think) from about 9" from the bottom and made two discharge nozzles out of 3/8" tubing and mounted them inside the upper part of the tank.
This unit uses soap obtained from the ZEP company, several types are available (rust remover, grease remover, and combinations of the two). Fill with water to cover the parts, about 2/3 up, and drop in your block or pair of heads.
This unit works as good as a commercial "Hot Tank" sometimes better, because I don't let the water get as dirty as commercial places do. Cleaning takes about 2 hrs.