The diesil method is probably the best way to break loose a frozen engine, What we used instead of a breaker bar was flat round plate with holes drilled in it to go into the pulley bolt holes. Then to that was welded a 5 foot piece of steel bar. Drop the pulley off bolt the tool to the balancer using all the bolts. Torque them down tight, then just slowly rock the bar back and forth untill you get a few full revolutions in. Then you should be able to turn it over with a normal breaker bar and socket.

Give the cylinders a good blow out with an airline. Spin the motor over with the starter motor with the plugs out, also at this time it is a good idea to check oil pressure. Maybe change your oil.

Heres 1 of my tricks, I dont know if you can get BRASSO over there, but it is a liquid metal polish. Once your engine is running air cleaner off, bring your revs up to 2000 or so, and just dribble and I do mean DRIBBLE about 5 CC's of metal polish at a time into the engine through the carb throat. DO NOT POUR IT IN, or you will get a BIG surprise and an engine rebuild for sure.
After you have used about 60 cc's thats 12 dribbles. let the engine on fast idle 800 to 1000 rpm for 15 minutes. Dont walfk away just stand there and listen to it, it should be smooth. Pour in some engine oil flush, let it run shut it down when ready and drain refill oil. That should fix it.