http://www.edelbrock.com/automotive_new/mc/carbs_acc/performer.shtml

500 cfm, Manual or Electric Choke
500 cfm, square-flange, electric choke (non-EGR)#1403
500 cfm, square-flange, manual choke (non-EGR) 	#1404* 	
CALIBRATED FOR PERFORMANCE
Designed and calibrated for small cubic-inch engines such as 305 c.i.d and smaller Chevrolet; 302 c.i.d. and smaller Ford and dual-quad applications such as Edelbrock C-26, F-28 and Street Tunnel Ram. Match with an Edelbrock Performer or Performer EPS manifold and other brands of similar design. Includes both timed and full vacuum ports for ignition advance. Comes with: Metering Jets – Primary .086, Secondary .095; Metering Rods – .065 x .052; Step-Up Spring – orange (5" Hg).

If you want an Economy 1403...
(From Edelbrock)
We do not want you to change jetting unless you can verify that your
engine is running rich. Try a set of #1463 metering rods to lean it out
about 4% or so. Thanks.

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600cfm
600 cfm, Street Legal, Electric Choke
600 cfm, square-flange, electric choke, (EGR)  	#1400*  	
CALIBRATED FOR FUEL ECONOMY
50-state street legal for all 1980 and earlier General Motors V8s (E.O. #D-215-10). Calibrated for maximum fuel economy. Includes timed vacuum ports, EGR and fuel vapor outlet. Not for computer-controlled engines. Comes with the following jets, rods and springs: Metering Jets – Primary .098, Secondary .095; Metering Rods – .073 x .047; Step-Up Spring – orange (5" Hg).

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600 cfm, square-flange, electric choke (non-EGR)  	#1405*
CALIBRATED FOR FUEL ECONOMY
Designed for small-block and small displacement big-block engines, these carbs are recommended only for stock to Performer level applications. They are not recommended for use on RPM or Torker II intake manifolds. Match with an Edelbrock Performer or Performer EPS manifold and other brands of similar design. Calibrated 2% leaner than #1405. Includes both timed and full vacuum ports for ignition advance. Comes with: Metering Jets – Primary .098, Secondary .095; Metering Rods – .075 x .047; Step-Up Spring – yellow (4" Hg). 

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600 cfm, square-flange, electric choke (non-EGR) 	#1406*
CALIBRATED FOR FUEL ECONOMY
Designed for small-block and small displacement big-block engines, these carbs are recommended only for stock to Performer level applications. They are not recommended for use on RPM or Torker II intake manifolds. Match with an Edelbrock Performer or Performer EPS manifold and other brands of similar design. Calibrated 2% leaner than #1405. Includes both timed and full vacuum ports for ignition advance. Comes with: Metering Jets – Primary .098, Secondary .095; Metering Rods – .075 x .047; Step-Up Spring – yellow (4" Hg). Use our Carb Stud Kits #8008 or #8024 if needed, see Installation Items. For auto trans throttle lever adapters and more, see Tuning Accessories.