Clamp a vise grip onto the flywheel ring gear and let it lock against the bellhousing to break the clutch plate bolts loose. You could also put the transmission in gear and set the parking brake or chock the wheels to lock the crankshaft. You'll need to put a bottle jack under the oil pan with a piece of wood to pad it and remove the flywheel, starter, and bell housing to get enough working room at the back of the block to change the freeze plug.

Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!