There were at LEAST 4 different springs used by Rochester on the 1973 Pontiac carbs.

Going from memory, they may all be the same length, but have different spring diameters, different number of turns, thus different operating characteristics.

I'm with Jerry on this one; although it would be easier to leave out the spring AND the step-up rods, and pretend it is a Holley! wink

Jon

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop