Do you have a certain HorsePower range in mind ? 
Do you have a Pontiac core engine available besides the matching # engine to build ? 
 
 
on side note - is the car a factory 400 4spd or a 403 Automatic ? 
 
Mainly that will just tell if you need a replacement air cleaner base. 
The 403 Olds is offset , if you go back with a Pontiac engine , you will need a base that is centered - not offset. 
Not that hard to find , just worth mentioning.
		 
		
		
		
		
		
		
		
		
	
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