I have no experience running Holleys in a dual setup but I have had 2 cars with dual Edelbrock 500 cfm carbs. Very easy to tune and ran great with no fuss no muss. If you want to run duals on a mild street engine and are an Edelbrock hater you are really causing more headaches for yourself. Not saying the Holleys dont work- just that its easier to get it right with the Carter type carbs. What ever brand you choose go BRAND NEW!!!!!!........ and go small. EXAMPLE- I have had 2 440 Challengers with 509 cams, 4:10 gears and 3000 stall converters. On the Eddy 2x4 manifold I ran 2 Edelbrock 500s when Eddy recommends 600s. It didnt miss a beat anywhere in the RPMs. That car now has an M1 Tunnel Ram with the same carbs. Car still runs fantastic but has more upper mid and high RPM due to the tunnel ram.