At the risk of sounding foolish,,, Since the engine is seized, and you have tried really hard to get it to rotate. Do you think you might break something else trying to get it freeded up? I have freed up a few engines, not many, just a few.. I usually have the heads off, and then lots of weasle piss, and a 4x4 block on the piston and a mallet. I dont just dive in aggresively, I look at it for a bit to make sure I wont hurt something, or myself .... I did this to an ENDT 673 2 years ago, and (2) John Deere 3179's in the last year. I new that I had new pistons and re-build kits, but I tried to be cautious.. When I got the pistons out, and tried to use my liner puller, non of the liners would move due to rust and age.. I welded beads inside the liners, to shrink them, then used my liner puller... anyway, Im just telling you what I did on 3 engines in recent years.. and with the heads off, you can see what condition it is in.. jojo