My combo is .222/.226 @ .050 hydraulic cam, home ported 351W 1.94/1.54 heads (not finished porting yet), edelbrock RPM intake, 9.5:1 compression, t-5, 3.73:1 gears in a 93 mustang. This is primarily a street car - i know that the double pumpers are worth about 10 hp over the vacuum secondary, but how is drivability? If the VS carb is more reliable, much better gas mileage, more driveable around town, it probably would be better for me. If there isn't much difference, I'll go with the DP for the power. BTW, i was going to go with a 650 cfm unit. This is my first carbed car, others were fuel injection, so any experience would be great. Thanks.