I went through Holley's carb selector program and if you key in 7,000 rpm max they want to sell you a 750. If you are really going to spin 8,000 like your cam is set up for, then Holley says to go with an 850 or possibly larger.
Holley doesn't think most people really want mechanical secondaries. The great thing about vacuum secondaries is that the carb won't over-fuel the motor so much. The secondaries will only open as much as the motor needs. Since you are planning to set the limiter at 7,000 rpm initially but your cam is set up for higher rpm, you might need more carb if you decide to raise the limiter. Unless there's a really good reason for staying with mechanical secondaries I think you should go with the vacuum secondaries, especially if as you say this is primarily a street-driven car.