the plate is accentric in that it'll only bolt on one way, in a certain bolt pattern.  Typically your entire engine should be balanced at the same time,..rods and pistons,...harmonic balancer, to flywheel.  Whoever balances it will probably drill precise holes in the plate. 
		
	
		
		
		
		
		
		
			
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				66 coupe: 351W 30 over.  Fiberglass shelby parts + flares
			 
		
		
		
		
		
		
	
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