Maybe you can disconnect the driveshaft at the center carrier (or rear axle) and use a spare, long length of metal. Drill 2 holes at one end of the metal and bolt it to the driveshaft. When you turn the crankshaft, the metal should brace against the ground to prevent the engine from turning. On my Toyota the crank pulley torque setting is over 200 Nm, so I had to extend my wrench with a 4 foot pipe and stand on it like Archimedes (engine was out of car).
If the head was still on the car, you could lower a rope into the cylinder via the sparkplug hole on the compression stroke. Feed the rope into the cylinder so the piston cannot compress to keep the engine from turning. Just be sure the rope is long enough that you can still pull it out, lol.
How I long for a shit brown wagon.