There's no way to get heat on the splines.
If the trans is trash and you don't care about it, then with the rear drive shaft disconnected and the bell housing unbolted I'd pry the two apart. There's a pot metal input shaft bearing retainer holding the input shaft in place that should break allowing the trans to be separated from the bell housing leaving the shaft and clutch still in place. It may take two men with something big like a digging/tunneling bar with lots of leverage working both sides at the same time to break it apart. Make sure you have the transmission supported from above so it doesn't crash down on you when it breaks free as nothing will be holding it up any longer.
Be safe...
Mike B
