What would be the likely DCR of a 1971 stage 1 iron headed ( basic porting gasket matching only ),455 ex a Riviera using stock 10 to 1 piston , stock bottom end , TA 284-88H cam installed 4 deg advanced with a intake closure at 37.5 deg as per cam card ? .Down in Aussie we use research octane rating, instead of your motor octane number , i am not sure of the conversion value but I'm thinking this may run on regular ?? Thank You Gentleman.