Small block and auto trans for my 66 Barracuda in Phoenix

It would be easier just to get the seized pistons free. What have you tried? ATF/Solvent and get a 24" breaker bar on the crank bolt. Just break the torque on the mains and rods so they are not helping the seizure..Move it up and down daily until the pistons free themselves, then pull and clean. Farm trick: Hang a sandbag or 2 on the breaker bar to give it constant tension overnight. It will eventually free itself, dont rush it or you could damage something. Dont beat on piston tops. If the crank is in a position to take a few caps off the driver bank and let the crank fight less than all 8 pistons, you could use that process to break a few at a time. Evaporust works great but wont penetrate oil. If everything is still dry, you could try that or cheap vinegar that is slightly acidic.