Marquis? Which vehicle has better horsepower and performance ratings? A 1975 Chevrolet, Nova? Or a 1984 Mercury, Grand Marquis? The Nova has a 308 with probably 6 cylinders and the Grand Marquis has a 351, with 8 cylinders.
if it was a 6 cylinder it would be a 250.305/307 are v8 engines.the 351 would be better more horsepower.the 308 engine that chevy made was only from 1966 to 1969 and had 325 horsepower but i don't think your nova has that engine in it.they also made a chevy 302 but they are very had to find.i would take the mercury.but then again i like fords.
The Mercury must be for Canada, 351 was only offered as o police model in Canada that year. Also, you may be mistaken about the Nova engine size. If it's a 6 cyl. original to that year it would be a 250. If it's a v8 305/350. To many questions to your question. Sorry