318 Carb Size Question

A 318 will use about a good 600 cfm at 6000 rpm. 650 @ 6500 rpm in moderate useage.
IMO, I think your choking it out with the 500 cfm carb, which would be fine it were a Hwy. geared people moved car. You know, just a ride to get grocery goods, church on Sunday, a drive on the Hwy. to the ball game, etc......

Even with that mild cam, a 600 is the min. size carb I would use. And I'll consider the rest of the engine as a stock-ish like set up. Like small valves 360 heads and headers with a 3.55 or less ratio.

What's the plan &'set up?