Hi again, It may also be sensible to remove the alternator and its ‘door’ from the L/H side of the engine, and the distributor/oil pump set-up from the R/H side. You will then be able to see which half of the engine has been starved of oil, and often this is confirmed by the big-end eye of the conrod and adjacent metal being ‘blued’ from the excessive heat that has been generated. Unless you are a fairly capable mechanic, it will then probably be best to hand the job over to a Scott specialist, because if a piston is seized badly it can be one hell of a job to get the cylinder barrel off the crankcase ! Applying hydraulic pressure into the affected cylinder, via the spark plug hole, may get the piston moving, but this can only work if the both the inlet and transfer ports are not open to the bore, ie. the stuck piston has to be well up the bore when it seized. If it is a really bad seizure it may be necessary to cut through the conrod with a plasma cutter or die grinder, to enable the barrel to be removed from the crankcase. Hammering on lengths of wooden dowel down the spark plug hole might just shift a seized piston, but is fraught with the risk of doing damage, and it really needs some past experience of how big a hammer, and how hard to wallop !
GOOD LUCK !!