I have 528 cubes, 440-1 heads, 15.1/1 compression and of four cam company's' recommendations, none are over 284 @ .050 on the intake, 292 exhaust, and most favor a 110 LSA. The current cam is 283/296 112 and didn't show much if any improvement over a 280/290/110 Isky I started with, that has only 197 at .200 intake lobe duration versus 203 minimum on the rest. All this tells me is that there is a very big diminishing return on duration after about 278 on the intake, and in your case you have less cubes and less compression. I am with the crowd that likes less duration. My 499 motor with 440-1 heads had a 283/290 Ultradyne in it, on a 110, and that one ran OK. My guess is you need to be about there or less.