Another 273 commando build .. This one will be a "BEAST"

Just landed another Clean 273 commando short block . short block is completely taken apart except for 6 pistons and rods .. crank is out . engine is with stock specs . all standard bearings .. I got 2 pistons out , rest are stuck.
Question is ...... what solvents are you guys using to free up these stuck pistons in the bores also ................ to loosen the rings in the piston lands ? I tried the blaster , tranny fluid , acetone couple other penetrating oils . I filled the bores (4 at a time ... on side ) with penetrating fluids and trans fluid to cover the 4 pistons in the bores and letting it sit for a while. Oh yeah..... I have one piston soaking in a gallon can of carb cleaner. Thanks !