I chose a 331 for reliabilty, I'd use a 347 if I was building a track car, but my car is for a daily driver.. I did not want to take the chances, plus 10-15 hp can be maid up with a power adder, so why worry about 10-15 hp.. That doesnt mean anything for a street car unless it was track car.. And since it is a street car why worry about it, you'll blow the doors off of 95 % of the cars on street.. Cops wont catch you :oD ... put on a A trim if funds are limited, thats 80-100 rwhp right there.. Your engine will love you !!